Foundry is a smart contract development toolchain.

Foundry manages your dependencies, compiles your project, runs tests, deploys, and lets you interact with the chain from the command-line and via Solidity scripts.

📖 Contributing

You can contribute to this book on GitHub.

Sections

Getting Started

To get started with Foundry, install Foundry and set up your first project.

Projects

This section will give you an overview of how to create and work with existing projects.

Forge Overview

The overview will give you all you need to know about how to use forge to develop, test, and deploy smart contracts.

Cast Overview

Learn how to use cast to interact with smart contracts, send transactions, and get chain data from the command-line.

Anvil Overview

Learn about anvil, Foundry's local node.

Chisel Overview

Learn how to use chisel, Foundry's integrated Solidity REPL.

Configuration

Guides on configuring Foundry.

Tutorials

Tutorials on building smart contracts with Foundry.

Contributing

Help us improve Foundry: Contributing

Appendix

References, troubleshooting, and more.

You can also check out Awesome Foundry, a curated list of awesome Foundry resources, tutorials, tools, and libraries!

Installation

If you face any issues while installing, check out the FAQ.

Precompiled binaries

Precompiled binaries are available from the GitHub releases page. These are better managed by using Foundryup.

Using Foundryup

Foundryup is the Foundry toolchain installer. You can find more about it here.

Open your terminal and run the following command:

curl -L https://foundry.paradigm.xyz | bash

This will install Foundryup, then simply follow the instructions on-screen, which will make the foundryup command available in your CLI.

Running foundryup by itself will install the latest (nightly) precompiled binaries: forge, cast, anvil, and chisel. See foundryup --help for more options, like installing from a specific version or commit.

ℹ️ Note

If you're on Windows, you will need to install and use Git BASH or WSL, as your terminal, since Foundryup currently does not support Powershell or Cmd.

Building from source

Prerequisites

You will need the Rust compiler and Cargo, the Rust package manager. The easiest way to install both is with rustup.rs.

On Windows, you will also need a recent version of Visual Studio, installed with the "Desktop Development With C++" Workloads option.

Building

You can either use the different Foundryup flags:

foundryup --branch master
foundryup --path path/to/foundry

Or, by using a single Cargo command:

cargo install --git https://github.com/foundry-rs/foundry --profile local --force foundry-cli anvil chisel

Or, by manually building from a local copy of the Foundry repository:

# clone the repository
git clone https://github.com/foundry-rs/foundry.git
cd foundry
# install Forge + Cast
cargo install --path ./cli --profile local --bins --force
# install Anvil
cargo install --path ./anvil --profile local --force
# install Chisel
cargo install --path ./chisel --profile local --force

Installing for CI in Github Action

See the foundry-rs/foundry-toolchain GitHub Action.

Using Foundry with Docker

Foundry can also be used entirely within a Docker container. If you don't have it, Docker can be installed directly from Docker's website.

Once installed, you can download the latest release by running:

docker pull ghcr.io/foundry-rs/foundry:latest

It is also possible to build the docker image locally. From the Foundry repository, run:

docker build -t foundry .

For examples and guides on using this image, see the Docker tutorial section.

ℹ️ Note

Some machines (including those with M1 chips) may be unable to build the docker image locally. This is a known issue.

First Steps with Foundry

This section provides an overview of the forge command line tool. We demonstrate how to create a new project, compile, and test it.

To start a new project with Foundry, use forge init:

$ forge init hello_foundry

Let's check out what forge generated for us:

$ cd hello_foundry
$ tree . -d -L 1
.
├── lib
├── script
├── src
└── test

4 directories

We can build the project with forge build:

$ forge build
Compiling 10 files with 0.8.16
Solc 0.8.16 finished in 3.97s
Compiler run successful

And run the tests with forge test:

$ forge test
No files changed, compilation skipped

Running 2 tests for test/Counter.t.sol:CounterTest
[PASS] testIncrement() (gas: 28312)
[PASS] testSetNumber(uint256) (runs: 256, μ: 27376, ~: 28387)
Test result: ok. 2 passed; 0 failed; finished in 24.43ms

💡 Tip

You can always print help for any subcommand (or their subcommands) by adding --help at the end.

You can watch these beginner tutorials if you are a visual learner.

Creating a New Project

To start a new project with Foundry, use forge init:

$ forge init hello_foundry

This creates a new directory hello_foundry from the default template. This also initializes a new git repository.

If you want to create a new project using a different template, you would pass the --template flag, like so:

$ forge init --template https://github.com/foundry-rs/forge-template hello_template

For now, let's check what the default template looks like:

$ cd hello_foundry
$ tree . -d -L 1
.
├── lib
├── script
├── src
└── test

4 directories

The default template comes with one dependency installed: Forge Standard Library. This is the preferred testing library used for Foundry projects. Additionally, the template also comes with an empty starter contract and a simple test.

Let's build the project:

$ forge build
Compiling 10 files with 0.8.16
Solc 0.8.16 finished in 3.97s
Compiler run successful

And run the tests:

$ forge test
No files changed, compilation skipped

Running 2 tests for test/Counter.t.sol:CounterTest
[PASS] testIncrement() (gas: 28312)
[PASS] testSetNumber(uint256) (runs: 256, μ: 27376, ~: 28387)
Test result: ok. 2 passed; 0 failed; finished in 24.43ms

You'll notice that two new directories have popped up: out and cache.

The out directory contains your contract artifact, such as the ABI, while the cache is used by forge to only recompile what is necessary.

Working on an Existing Project

If you download an existing project that uses Foundry, it is really easy to get going.

First, get the project from somewhere. In this example, we will clone the femplate repository from GitHub:

$ git clone https://github.com/abigger87/femplate
$ cd femplate
$ forge install

We run forge install to install the submodule dependencies that are in the project.

To build, use forge build:

$ forge build
Compiling 10 files with 0.8.15
Solc 0.8.15 finished in 4.35s
Compiler run successful

And to test, use forge test:

$ forge test
No files changed, compilation skipped

Running 1 test for test/Greeter.t.sol:GreeterTest
[PASS] testSetGm() (gas: 107402)
Test result: ok. 1 passed; 0 failed; finished in 4.77ms

Dependencies

Forge manages dependencies using git submodules by default, which means that it works with any GitHub repository that contains smart contracts.

Adding a dependency

To add a dependency, run forge install:

$ forge install transmissions11/solmate
Installing solmate in "/private/var/folders/p_/xbvs4ns92wj3b9xmkc1zkw2w0000gn/T/tmp.FRH0gNvz/deps/lib/solmate" (url: Some("https://github.com/transmissions11/solmate"), tag: None)
    Installed solmate

This pulls the solmate library, stages the .gitmodules file in git and makes a commit with the message "Installed solmate".

If we now check the lib folder:

$ tree lib -L 1
lib
├── forge-std
├── solmate
└── weird-erc20

3 directories, 0 files

We can see that Forge installed solmate!

By default, forge install installs the latest master branch version. If you want to install a specific tag or commit, you can do it like so:

$ forge install transmissions11/solmate@v7

Remapping dependencies

Forge can remap dependencies to make them easier to import. Forge will automatically try to deduce some remappings for you:

$ forge remappings
ds-test/=lib/forge-std/lib/ds-test/src/
forge-std/=lib/forge-std/src/
solmate/=lib/solmate/src/
weird-erc20/=lib/weird-erc20/src/

These remappings mean:

To import from forge-std we would write: import "forge-std/Contract.sol";
To import from ds-test we would write: import "ds-test/Contract.sol";
To import from solmate we would write: import "solmate/Contract.sol";
To import from weird-erc20 we would write: import "weird-erc20/Contract.sol";

You can customize these remappings by creating a remappings.txt file in the root of your project.

Let's create a remapping called solmate-utils that points to the utils folder in the solmate repository!

solmate-utils/=lib/solmate/src/utils/

You can also set remappings in foundry.toml.

remappings = [
    "@solmate-utils/=lib/solmate/src/utils/",
]

Now we can import any of the contracts in src/utils of the solmate repository like so:

import "solmate-utils/LibString.sol";

Updating dependencies

You can update a specific dependency to the latest commit on the version you have specified using forge update <dep>. For example, if we wanted to pull the latest commit from our previously installed master-version of solmate, we would run:

$ forge update lib/solmate

Alternatively, you can do this for all dependencies at once by just running forge update.

Removing dependencies

You can remove dependencies using forge remove <deps>..., where <deps> is either the full path to the dependency or just the name. For example, to remove solmate both of these commands are equivalent:

$ forge remove solmate
# ... is equivalent to ...
$ forge remove lib/solmate

Hardhat compatibility

Forge also supports Hardhat-style projects where dependencies are npm packages (stored in node_modules) and contracts are stored in contracts as opposed to src.

To enable Hardhat compatibility mode pass the --hh flag.

Project Layout

Forge is flexible on how you structure your project. By default, the structure is:

.
├── foundry.toml
├── lib
│   └── forge-std
│       ├── LICENSE-APACHE
│       ├── LICENSE-MIT
│       ├── README.md
│       ├── foundry.toml
│       ├── lib
│       └── src
├── script
│   └── Counter.s.sol
├── src
│   └── Counter.sol
└── test
    └── Counter.t.sol

7 directories, 8 files

You can configure Foundry's behavior using foundry.toml.
Remappings are specified in remappings.txt.
The default directory for contracts is src/.
The default directory for tests is test/, where any contract with a function that starts with test is considered to be a test.
Dependencies are stored as git submodules in lib/.

You can configure where Forge looks for both dependencies and contracts using the --lib-paths and --contracts flags respectively. Alternatively you can configure it in foundry.toml.

Combined with remappings, this gives you the flexibility needed to support the project structure of other toolchains such as Hardhat and Truffle.

For automatic Hardhat support you can also pass the --hh flag, which sets the following flags: --lib-paths node_modules --contracts contracts.

Overview of Forge

Forge is a command-line tool that ships with Foundry. Forge tests, builds, and deploys your smart contracts.

Tests

Forge can run your tests with the forge test command. All tests are written in Solidity.

Forge will look for the tests anywhere in your source directory. Any contract with a function that starts with test is considered to be a test. Usually, tests will be placed in test/ by convention and end with .t.sol.

Here's an example of running forge test in a freshly created project, that only has the default test:

$ forge test
No files changed, compilation skipped

Running 2 tests for test/Counter.t.sol:CounterTest
[PASS] testIncrement() (gas: 28312)
[PASS] testSetNumber(uint256) (runs: 256, μ: 27376, ~: 28387)
Test result: ok. 2 passed; 0 failed; finished in 24.43ms

You can also run specific tests by passing a filter:

$ forge test --match-contract ComplicatedContractTest --match-test testDeposit
Compiling 7 files with 0.8.10
Solc 0.8.10 finished in 4.20s
Compiler run successful

Running 2 tests for test/ComplicatedContract.t.sol:ComplicatedContractTest
[PASS] testDepositERC20() (gas: 102237)
[PASS] testDepositETH() (gas: 61458)
Test result: ok. 2 passed; 0 failed; finished in 1.05ms

This will run the tests in the ComplicatedContractTest test contract with testDeposit in the name. Inverse versions of these flags also exist (--no-match-contract and --no-match-test).

You can run tests in filenames that match a glob pattern with --match-path.

$ forge test --match-path test/ContractB.t.sol
No files changed, compilation skipped

Running 1 test for test/ContractB.t.sol:ContractBTest
[PASS] testExample() (gas: 257)
Test result: ok. 1 passed; 0 failed; finished in 492.35µs

The inverse of the --match-path flag is --no-match-path.

Logs and traces

The default behavior for forge test is to only display a summary of passing and failing tests. You can control this behavior by increasing the verbosity (using the -v flag). Each level of verbosity adds more information:

Level 2 (-vv): Logs emitted during tests are also displayed. That includes assertion errors from tests, showing information such as expected vs actual.
Level 3 (-vvv): Stack traces for failing tests are also displayed.
Level 4 (-vvvv): Stack traces for all tests are displayed, and setup traces for failing tests are displayed.
Level 5 (-vvvvv): Stack traces and setup traces are always displayed.

Watch mode

Forge can re-run your tests when you make changes to your files using forge test --watch.

By default, only changed test files are re-run. If you want to re-run all tests on a change, you can use forge test --watch --run-all.

Writing Tests

Tests are written in Solidity. If the test function reverts, the test fails, otherwise it passes.

Let's go over the most common way of writing tests, using the Forge Standard Library's Test contract, which is the preferred way of writing tests with Forge.

In this section, we'll go over the basics using the functions from the Forge Std's Test contract, which is itself a superset of DSTest. You will learn how to use more advanced stuff from the Forge Standard Library soon.

DSTest provides basic logging and assertion functionality. To get access to the functions, import forge-std/Test.sol and inherit from Test in your test contract:

import "forge-std/Test.sol";

Let's examine a basic test:

pragma solidity 0.8.10;

import "forge-std/Test.sol";

contract ContractBTest is Test {
    uint256 testNumber;

    function setUp() public {
        testNumber = 42;
    }

    function test_NumberIs42() public {
        assertEq(testNumber, 42);
    }

    function testFail_Subtract43() public {
        testNumber -= 43;
    }
}

Forge uses the following keywords in tests:

setUp: An optional function invoked before each test case is run.
```
function setUp() public {
    testNumber = 42;
}
```

test: Functions prefixed with test are run as a test case.

function test_NumberIs42() public {
    assertEq(testNumber, 42);
}

testFail: The inverse of the test prefix - if the function does not revert, the test fails.
```
function testFail_Subtract43() public {
    testNumber -= 43;
}
```
A good practice is to use the pattern test_Revert[If|When]_Condition in combination with the expectRevert cheatcode (cheatcodes are explained in greater detail in the following section). Also, other testing practices can be found in the Tutorials section. Now, instead of using testFail, you know exactly what reverted and with which error:
```
function test_CannotSubtract43() public {
    vm.expectRevert(stdError.arithmeticError);
    testNumber -= 43;
}
```

Tests are deployed to 0xb4c79daB8f259C7Aee6E5b2Aa729821864227e84. If you deploy a contract within your test, then 0xb4c...7e84 will be its deployer. If the contract deployed within a test gives special permissions to its deployer, such as Ownable.sol's onlyOwner modifier, then the test contract 0xb4c...7e84 will have those permissions.

⚠️ Note

Test functions must have either external or public visibility. Functions declared as internal or private won't be picked up by Forge, even if they are prefixed with test.

Shared setups

It is possible to use shared setups by creating helper abstract contracts and inheriting them in your test contracts:

abstract contract HelperContract {
    address constant IMPORTANT_ADDRESS = 0x543d...;
    SomeContract someContract;
    constructor() {...}
}

contract MyContractTest is Test, HelperContract {
    function setUp() public {
        someContract = new SomeContract(0, IMPORTANT_ADDRESS);
        ...
    }
}

contract MyOtherContractTest is Test, HelperContract {
    function setUp() public {
        someContract = new SomeContract(1000, IMPORTANT_ADDRESS);
        ...
    }
}

💡 Tip

Use the getCode cheatcode to deploy contracts with incompatible Solidity versions.

Cheatcodes

Most of the time, simply testing your smart contracts outputs isn't enough. To manipulate the state of the blockchain, as well as test for specific reverts and events, Foundry is shipped with a set of cheatcodes.

Cheatcodes allow you to change the block number, your identity, and more. They are invoked by calling specific functions on a specially designated address: 0x7109709ECfa91a80626fF3989D68f67F5b1DD12D.

You can access cheatcodes easily via the vm instance available in Forge Standard Library's Test contract. Forge Standard Library is explained in greater detail in the following section.

Let's write a test for a smart contract that is only callable by its owner.

pragma solidity 0.8.10;

import "forge-std/Test.sol";

error Unauthorized();

contract OwnerUpOnly {
    address public immutable owner;
    uint256 public count;

    constructor() {
        owner = msg.sender;
    }

    function increment() external {
        if (msg.sender != owner) {
            revert Unauthorized();
        }
        count++;
    }
}

contract OwnerUpOnlyTest is Test {
    OwnerUpOnly upOnly;

    function setUp() public {
        upOnly = new OwnerUpOnly();
    }

    function test_IncrementAsOwner() public {
        assertEq(upOnly.count(), 0);
        upOnly.increment();
        assertEq(upOnly.count(), 1);
    }
}

If we run forge test now, we will see that the test passes, since OwnerUpOnlyTest is the owner of OwnerUpOnly.

$ forge test
Compiling 7 files with 0.8.10
Solc 0.8.10 finished in 4.25s
Compiler run successful

Running 1 test for test/OwnerUpOnly.t.sol:OwnerUpOnlyTest
[PASS] testIncrementAsOwner() (gas: 29162)
Test result: ok. 1 passed; 0 failed; finished in 928.64µs

Let's make sure that someone who is definitely not the owner can't increment the count:

contract OwnerUpOnlyTest is Test {
    OwnerUpOnly upOnly;

    // ...

    function testFail_IncrementAsNotOwner() public {
        vm.prank(address(0));
        upOnly.increment();
    }
}

If we run forge test now, we will see that all the test pass.

$ forge test
No files changed, compilation skipped

Running 2 tests for test/OwnerUpOnly.t.sol:OwnerUpOnlyTest
[PASS] testFailIncrementAsNotOwner() (gas: 8413)
[PASS] testIncrementAsOwner() (gas: 29162)
Test result: ok. 2 passed; 0 failed; finished in 1.03ms

The test passed because the prank cheatcode changed our identity to the zero address for the next call (upOnly.increment()). The test case passed since we used the testFail prefix, however, using testFail is considered an anti-pattern since it does not tell us anything about why upOnly.increment() reverted.

If we run the tests again with traces turned on, we can see that we reverted with the correct error message.

$ forge test -vvvv --match-test testFail_IncrementAsNotOwner
No files changed, compilation skipped

Running 1 test for test/OwnerUpOnly.t.sol:OwnerUpOnlyTest
[PASS] testFailIncrementAsNotOwner() (gas: 8413)
Traces:
  [8413] OwnerUpOnlyTest::testFailIncrementAsNotOwner() 
    ├─ [0] VM::prank(0x0000000000000000000000000000000000000000) 
    │   └─ ← ()
    ├─ [247] 0xce71…c246::increment() 
    │   └─ ← 0x82b42900
    └─ ← 0x82b42900

Test result: ok. 1 passed; 0 failed; finished in 2.01ms

To be sure in the future, let's make sure that we reverted because we are not the owner using the expectRevert cheatcode:

contract OwnerUpOnlyTest is Test {
    OwnerUpOnly upOnly;

    // ...

    // Notice that we replaced `testFail` with `test`
    function test_RevertWhen_CallerIsNotOwner() public {
        vm.expectRevert(Unauthorized.selector);
        vm.prank(address(0));
        upOnly.increment();
    }
}

If we run forge test one last time, we see that the test still passes, but this time we are sure that it will always fail if we revert for any other reason.

$ forge test
No files changed, compilation skipped

Running 2 tests for test/OwnerUpOnly.t.sol:OwnerUpOnlyTest
[PASS] testIncrementAsNotOwner() (gas: 8739)
[PASS] testIncrementAsOwner() (gas: 29162)
Test result: ok. 2 passed; 0 failed; finished in 1.15ms

Another cheatcode that is perhaps not so intuitive is the expectEmit function. Before looking at expectEmit, we need to understand what an event is.

Events are inheritable members of contracts. When you emit an event, the arguments are stored on the blockchain. The indexed attribute can be added to a maximum of three parameters of an event to form a data structure known as a "topic." Topics allow users to search for events on the blockchain.

pragma solidity 0.8.10;

import "forge-std/Test.sol";

contract EmitContractTest is Test {
    event Transfer(address indexed from, address indexed to, uint256 amount);

    function test_ExpectEmit() public {
        ExpectEmit emitter = new ExpectEmit();
        // Check that topic 1, topic 2, and data are the same as the following emitted event.
        // Checking topic 3 here doesn't matter, because `Transfer` only has 2 indexed topics.
        vm.expectEmit(true, true, false, true);
        // The event we expect
        emit Transfer(address(this), address(1337), 1337);
        // The event we get
        emitter.t();
    }

    function test_ExpectEmit_DoNotCheckData() public {
        ExpectEmit emitter = new ExpectEmit();
        // Check topic 1 and topic 2, but do not check data
        vm.expectEmit(true, true, false, false);
        // The event we expect
        emit Transfer(address(this), address(1337), 1338);
        // The event we get
        emitter.t();
    }
}

contract ExpectEmit {
    event Transfer(address indexed from, address indexed to, uint256 amount);

    function t() public {
        emit Transfer(msg.sender, address(1337), 1337);
    }
}

When we call vm.expectEmit(true, true, false, true);, we want to check the 1st and 2nd indexed topic for the next event.

The expected Transfer event in test_ExpectEmit() means we are expecting that from is address(this), and to is address(1337). This is compared against the event emitted from emitter.t().

In other words, we are checking that the first topic from emitter.t() is equal to address(this). The 3rd argument in expectEmit is set to false because there is no need to check the third topic in the Transfer event, since there are only two. It does not matter even if we set to true.

The 4th argument in expectEmit is set to true, which means that we want to check "non-indexed topics", also known as data.

For example, we want the data from the expected event in test_ExpectEmit - which is amount - to equal to the data in the actual emitted event. In other words, we are asserting that amount emitted by emitter.t() is equal to 1337. If the fourth argument in expectEmit was set to false, we would not check amount.

In other words, test_ExpectEmit_DoNotCheckData is a valid test case, even though the amounts differ, since we do not check the data.

📚 Reference

See the Cheatcodes Reference for a complete overview of all the available cheatcodes.

Forge Standard Library Overview

Forge Standard Library (Forge Std for short) is a collection of helpful contracts that make writing tests easier, faster, and more user-friendly.

Using Forge Std is the preferred way of writing tests with Foundry.

It provides all the essential functionality you need to get started writing tests:

Vm.sol: Up-to-date cheatcodes interface
console.sol and console2.sol: Hardhat-style logging functionality
Script.sol: Basic utilities for Solidity scripting
Test.sol: A superset of DSTest containing standard libraries, a cheatcodes instance (vm), and Hardhat console

Simply import Test.sol and inherit from Test in your test contract:

import "forge-std/Test.sol";

contract ContractTest is Test { ...

Now, you can:

// Access Hevm via the `vm` instance
vm.startPrank(alice);

// Assert and log using Dappsys Test
assertEq(dai.balanceOf(alice), 10000e18);

// Log with the Hardhat `console` (`console2`)
console.log(alice.balance);

// Use anything from the Forge Std std-libraries
deal(address(dai), alice, 10000e18);

To import the Vm interface or the console library individually:

import "forge-std/Vm.sol";

import "forge-std/console.sol";

Note: console2.sol contains patches to console.sol that allows Forge to decode traces for calls to the console, but it is not compatible with Hardhat.

import "forge-std/console2.sol";

Standard libraries

Forge Std currently consists of six standard libraries.

Std Logs

Std Logs expand upon the logging events from the DSTest library.

Std Assertions

Std Assertions expand upon the assertion functions from the DSTest library.

Std Cheats

Std Cheats are wrappers around Forge cheatcodes that make them safer to use and improve the DX.

You can access Std Cheats by simply calling them inside your test contract, as you would any other internal function:

// set up a prank as Alice with 100 ETH balance
hoax(alice, 100 ether);

Std Errors

Std Errors provide wrappers around common internal Solidity errors and reverts.

Std Errors are most useful in combination with the expectRevert cheatcode, as you do not need to remember the internal Solidity panic codes yourself. Note that you have to access them through stdError, as this is a library.

// expect an arithmetic error on the next call (e.g. underflow)
vm.expectRevert(stdError.arithmeticError);

Std Storage

Std Storage makes manipulating contract storage easy. It can find and write to the storage slot(s) associated with a particular variable.

The Test contract already provides a StdStorage instance stdstore through which you can access any std-storage functionality. Note that you must add using stdStorage for StdStorage in your test contract first.

// find the variable `score` in the contract `game`
// and change its value to 10
stdstore
    .target(address(game))
    .sig(game.score.selector)
    .checked_write(10);

Std Math

Std Math is a library with useful mathematical functions that are not provided in Solidity.

Note that you have to access them through stdMath, as this is a library.

// get the absolute value of -10
uint256 ten = stdMath.abs(-10)

📚 Reference

See the Forge Standard Library Reference for a complete overview of Forge Standard Library.

Understanding Traces

Forge can produce traces either for failing tests (-vvv) or all tests (-vvvv).

Traces follow the same general format:

  [<Gas Usage>] <Contract>::<Function>(<Parameters>)
    ├─ [<Gas Usage>] <Contract>::<Function>(<Parameters>)
    │   └─ ← <Return Value>
    └─ ← <Return Value>

Each trace can have many more subtraces, each denoting a call to a contract and a return value.

If your terminal supports color, the traces will also come with a variety of colors:

Green: For calls that do not revert
Red: For reverting calls
Blue: For calls to cheat codes
Cyan: For emitted logs
Yellow: For contract deployments

The gas usage (marked in square brackets) is for the entirety of the function call. You may notice, however, that sometimes the gas usage of one trace does not exactly match the gas usage of all its subtraces:

  [24661] OwnerUpOnlyTest::testIncrementAsOwner()
    ├─ [2262] OwnerUpOnly::count()
    │   └─ ← 0
    ├─ [20398] OwnerUpOnly::increment()
    │   └─ ← ()
    ├─ [262] OwnerUpOnly::count()
    │   └─ ← 1
    └─ ← ()

The gas unaccounted for is due to some extra operations happening between calls, such as arithmetic and store reads/writes.

Forge will try to decode as many signatures and values as possible, but sometimes this is not possible. In these cases, the traces will appear like so:

  [<Gas Usage>] <Address>::<Calldata>
    └─ ← <Return Data>

Fork Testing

Forge supports testing in a forked environment with two different approaches:

Forking Mode — use a single fork for all your tests via the forge test --fork-url flag
Forking Cheatcodes — create, select, and manage multiple forks directly in Solidity test code via forking cheatcodes

Which approach to use? Forking mode affords running an entire test suite against a specific forked environment, while forking cheatcodes provide more flexibility and expressiveness to work with multiple forks in your tests. Your particular use case and testing strategy will help inform which approach to use.

Forking Mode

To run all tests in a forked environment, such as a forked Ethereum mainnet, pass an RPC URL via the --fork-url flag:

forge test --fork-url <your_rpc_url>

The following values are changed to reflect those of the chain at the moment of forking:

It is possible to specify a block from which to fork with --fork-block-number:

forge test --fork-url <your_rpc_url> --fork-block-number 1

Forking is especially useful when you need to interact with existing contracts. You may choose to do integration testing this way, as if you were on an actual network.

Caching

If both --fork-url and --fork-block-number are specified, then data for that block is cached for future test runs.

The data is cached in ~/.foundry/cache/rpc/<chain name>/<block number>. To clear the cache, simply remove the directory or run forge clean (removes all build artifacts and cache directories).

It is also possible to ignore the cache entirely by passing --no-storage-caching, or with foundry.toml by configuring no_storage_caching and rpc_storage_caching.

Improved traces

Forge supports identifying contracts in a forked environment with Etherscan.

To use this feature, pass the Etherscan API key via the --etherscan-api-key flag:

forge test --fork-url <your_rpc_url> --etherscan-api-key <your_etherscan_api_key>

Alternatively, you can set the ETHERSCAN_API_KEY environment variable.

Forking Cheatcodes

Forking cheatcodes allow you to enter forking mode programatically in your Solidity test code. Instead of configuring forking mode via forge CLI arguments, these cheatcodes allow you to use forking mode on a test-by-test basis and work with multiple forks in your tests. Each fork is identified via its own unique uint256 identifier.

Usage

Important to keep in mind that all test functions are isolated, meaning each test function is executed with a copy of the state after setUp and is executed in its own stand-alone EVM.

Therefore forks created during setUp are available in tests. The code example below uses createFork to create two forks, but does not select one initially. Each fork is identified with a unique identifier (uint256 forkId), which is assigned when it is first created.

Enabling a specific fork is done via passing that forkId to selectFork.

createSelectFork is a one-liner for createFork plus selectFork.

There can only be one fork active at a time, and the identifier for the currently active fork can be retrieved via activeFork.

Similar to roll, you can set block.number of a fork with rollFork.

To understand what happens when a fork is selected, it is important to know how the forking mode works in general:

Each fork is a standalone EVM, i.e. all forks use completely independent storage. The only exception is the state of the msg.sender and the test contract itself, which are persistent across fork swaps. In other words all changes that are made while fork A is active (selectFork(A)) are only recorded in fork A's storage and are not available if another fork is selected. However, changes recorded in the test contract itself (variables) are still available because the test contract is a persistent account.

The selectFork cheatcode sets the remote section with the fork's data source, however the local memory remains persistent across fork swaps. This also means selectFork can be called at all times with any fork, to set the remote data source. However, it is important to keep in mind the above rules for read/write access always apply, meaning writes are persistent across fork swaps.

Examples

Create and Select Forks

contract ForkTest is Test {
    // the identifiers of the forks
    uint256 mainnetFork;
    uint256 optimismFork;
    
    //Access variables from .env file via vm.envString("varname")
    //Replace ALCHEMY_KEY by your alchemy key or Etherscan key, change RPC url if need
    //inside your .env file e.g: 
    //MAINNET_RPC_URL = 'https://eth-mainnet.g.alchemy.com/v2/ALCHEMY_KEY'
    //string MAINNET_RPC_URL = vm.envString("MAINNET_RPC_URL");
    //string OPTIMISM_RPC_URL = vm.envString("OPTIMISM_RPC_URL");

    // create two _different_ forks during setup
    function setUp() public {
        mainnetFork = vm.createFork(MAINNET_RPC_URL);
        optimismFork = vm.createFork(OPTIMISM_RPC_URL);
    }

    // demonstrate fork ids are unique
    function testForkIdDiffer() public {
        assert(mainnetFork != optimismFork);
    }

    // select a specific fork
    function testCanSelectFork() public {
        // select the fork
        vm.selectFork(mainnetFork);
        assertEq(vm.activeFork(), mainnetFork);

        // from here on data is fetched from the `mainnetFork` if the EVM requests it and written to the storage of `mainnetFork`
    }

    // manage multiple forks in the same test
    function testCanSwitchForks() public {
        vm.selectFork(mainnetFork);
        assertEq(vm.activeFork(), mainnetFork);

        vm.selectFork(optimismFork);
        assertEq(vm.activeFork(), optimismFork);
    }

    // forks can be created at all times
    function testCanCreateAndSelectForkInOneStep() public {
        // creates a new fork and also selects it
        uint256 anotherFork = vm.createSelectFork(MAINNET_RPC_URL);
        assertEq(vm.activeFork(), anotherFork);
    }

    // set `block.number` of a fork
    function testCanSetForkBlockNumber() public {
        vm.selectFork(mainnetFork);
        vm.rollFork(1_337_000);

        assertEq(block.number, 1_337_000);
    }
}

Separated and persistent storage

As mentioned each fork is essentially an independent EVM with separated storage.

Only the accounts of msg.sender and the test contract (ForkTest) are persistent when forks are selected. But any account can be turned into a persistent account: makePersistent.

An account that is persistent is unique, i.e. it exists on all forks

contract ForkTest is Test {
    // the identifiers of the forks
    uint256 mainnetFork;
    uint256 optimismFork;
    
    //Access variables from .env file via vm.envString("varname")
    //Replace ALCHEMY_KEY by your alchemy key or Etherscan key, change RPC url if need
    //inside your .env file e.g: 
    //MAINNET_RPC_URL = 'https://eth-mainnet.g.alchemy.com/v2/ALCHEMY_KEY'
    //string MAINNET_RPC_URL = vm.envString("MAINNET_RPC_URL");
    //string OPTIMISM_RPC_URL = vm.envString("OPTIMISM_RPC_URL");

    // create two _different_ forks during setup
    function setUp() public {
        mainnetFork = vm.createFork(MAINNET_RPC_URL);
        optimismFork = vm.createFork(OPTIMISM_RPC_URL);
    }

    // creates a new contract while a fork is active
    function testCreateContract() public {
        vm.selectFork(mainnetFork);
        assertEq(vm.activeFork(), mainnetFork);
        
        // the new contract is written to `mainnetFork`'s storage
        SimpleStorageContract simple = new SimpleStorageContract();
        
        // and can be used as normal
        simple.set(100);
        assertEq(simple.value(), 100);
        
        // after switching to another contract we still know `address(simple)` but the contract only lives in `mainnetFork` 
        vm.selectFork(optimismFork);
        
        /* this call will therefore revert because `simple` now points to a contract that does not exist on the active fork
        * it will produce following revert message:
        * 
        * "Contract 0xCe71065D4017F316EC606Fe4422e11eB2c47c246 does not exist on active fork with id `1`
        *       But exists on non active forks: `[0]`"
        */
        simple.value();
    }
    
     // creates a new _persistent_ contract while a fork is active
     function testCreatePersistentContract() public {
        vm.selectFork(mainnetFork);
        SimpleStorageContract simple = new SimpleStorageContract();
        simple.set(100);
        assertEq(simple.value(), 100);
        
        // mark the contract as persistent so it is also available when other forks are active
        vm.makePersistent(address(simple));
        assert(vm.isPersistent(address(simple))); 
        
        vm.selectFork(optimismFork);
        assert(vm.isPersistent(address(simple))); 
        
        // This will succeed because the contract is now also available on the `optimismFork`
        assertEq(simple.value(), 100);
     }
}

contract SimpleStorageContract {
    uint256 public value;

    function set(uint256 _value) public {
        value = _value;
    }
}

For more details and examples, see the forking cheatcodes reference.

Advanced Testing

Forge comes with a number of advanced testing methods:

In the future, Forge will also support these:

Each chapter dives into what problem the testing methods solve, and how to apply them to your own project.

Fuzz Testing

Forge supports property based testing.

Property-based testing is a way of testing general behaviors as opposed to isolated scenarios.

Let's examine what that means by writing a unit test, finding the general property we are testing for, and converting it to a property-based test instead:

pragma solidity 0.8.10;

import "forge-std/Test.sol";

contract Safe {
    receive() external payable {}

    function withdraw() external {
        payable(msg.sender).transfer(address(this).balance);
    }
}

contract SafeTest is Test {
    Safe safe;

    // Needed so the test contract itself can receive ether
    // when withdrawing
    receive() external payable {}

    function setUp() public {
        safe = new Safe();
    }

    function test_Withdraw() public {
        payable(address(safe)).transfer(1 ether);
        uint256 preBalance = address(this).balance;
        safe.withdraw();
        uint256 postBalance = address(this).balance;
        assertEq(preBalance + 1 ether, postBalance);
    }
}

Running the test, we see it passes:

$ forge test
Compiling 6 files with 0.8.10
Solc 0.8.10 finished in 3.78s
Compiler run successful

Running 1 test for test/Safe.t.sol:SafeTest
[PASS] testWithdraw() (gas: 19462)
Test result: ok. 1 passed; 0 failed; finished in 873.70µs

This unit test does test that we can withdraw ether from our safe. However, who is to say that it works for all amounts, not just 1 ether?

The general property here is: given a safe balance, when we withdraw, we should get whatever is in the safe.

Forge will run any test that takes at least one parameter as a property-based test, so let's rewrite:

contract SafeTest is Test {
    // ...

    function testFuzz_Withdraw(uint256 amount) public {
        payable(address(safe)).transfer(amount);
        uint256 preBalance = address(this).balance;
        safe.withdraw();
        uint256 postBalance = address(this).balance;
        assertEq(preBalance + amount, postBalance);
    }
}

If we run the test now, we can see that Forge runs the property-based test, but it fails for high values of amount:

$ forge test
Compiling 1 files with 0.8.10
Solc 0.8.10 finished in 1.69s
Compiler run successful

Running 1 test for test/Safe.t.sol:SafeTest
[FAIL. Reason: EvmError: Revert Counterexample: calldata=0x215a2f200000000000000000000000000000000000000001000000000000000000000000, args=[79228162514264337593543950336]] testWithdraw(uint256) (runs: 47, μ: 19554, ~: 19554)
Test result: FAILED. 0 passed; 1 failed; finished in 8.75ms

The default amount of ether that the test contract is given is 2**96 wei (as in DappTools), so we have to restrict the type of amount to uint96 to make sure we don't try to send more than we have:

    function testFuzz_Withdraw(uint96 amount) public {

And now it passes:

$ forge test
Compiling 1 files with 0.8.10
Solc 0.8.10 finished in 1.67s
Compiler run successful

Running 1 test for test/Safe.t.sol:SafeTest
[PASS] testWithdraw(uint96) (runs: 256, μ: 19078, ~: 19654)
Test result: ok. 1 passed; 0 failed; finished in 19.56ms

You may want to exclude certain cases using the assume cheatcode. In those cases, fuzzer will discard the inputs and start a new fuzz run:

function testFuzz_Withdraw(uint96 amount) public {
    vm.assume(amount > 0.1 ether);
    // snip
}

There are different ways to run property-based tests, notably parametric testing and fuzzing. Forge only supports fuzzing.

Interpreting results

You might have noticed that fuzz tests are summarized a bit differently compared to unit tests:

"runs" refers to the amount of scenarios the fuzzer tested. By default, the fuzzer will generate 256 scenarios, but this and other test execution parameters can be setup by the user. Fuzzer configuration details are provided here.
"μ" (Greek letter mu) is the mean gas used across all fuzz runs
"~" (tilde) is the median gas used across all fuzz runs

Configuring fuzz test execution

Fuzz tests execution is governed by parameters that can be controlled by users via Forge configuration primitives. Configs can be applied globally or on a per-test basis. For details on this topic please refer to 📚 Global config and 📚 In-line config.

Invariant Testing

Overview

Invariant testing allows for a set of invariant expressions to be tested against randomized sequences of pre-defined function calls from pre-defined contracts. After each function call is performed, all defined invariants are asserted.

Invariant testing is a powerful tool to expose incorrect logic in protocols. Due to the fact that function call sequences are randomized and have fuzzed inputs, invariant testing can expose false assumptions and incorrect logic in edge cases and highly complex protocol states.

Invariant testing campaigns have two dimensions, runs and depth:

runs: Number of times that a sequence of function calls is generated and run.
depth: Number of function calls made in a given run. All defined invariants are asserted after each function call is made. If a function call reverts, the depth counter still increments.

These and other invariant configuration aspects are explained here.

Similar to how standard tests are run in Foundry by prefixing a function name with test, invariant tests are denoted by prefixing the function name with invariant (e.g., function invariant_A()).

Configuring invariant test execution

Invariant tests execution is governed by parameters that can be controlled by users via Forge configuration primitives. Configs can be applied globally or on a per-test basis. For details on this topic please refer to 📚 Global config and 📚 In-line config.

Defining Invariants

Invariants are conditions expressions that should always hold true over the course of a fuzzing campaign. A good invariant testing suite should have as many invariants as possible, and can have different testing suites for different protocol states.

Examples of invariants are:

"The xy=k formula always holds" for Uniswap
"The sum of all user balances is equal to the total supply" for an ERC-20 token.

There are different ways to assert invariants, as outlined in the table below:

Type	Explanation	Example
Direct assertions	Query a protocol smart contract and assert values are as expected.	`assertGe( token.totalAssets(), token.totalSupply() )`
Ghost variable assertions	Query a protocol smart contract and compare it against a value that has been persisted in the test environment (ghost variable).	`assertEq( token.totalSupply(), sumBalanceOf )`
Deoptimizing (Naive implementation assertions)	Query a protocol smart contract and compare it against a naive and typically highly gas-inefficient implementation of the same desired logic.	`assertEq( pool.outstandingInterest(), test.naiveInterest() )`

Conditional Invariants

Invariants must hold over the course of a given fuzzing campaign, but that doesn't mean they must hold true in every situation. There is the possibility for certain invariants to be introduced/removed in a given scenario (e.g., during a liquidation).

It is not recommended to introduce conditional logic into invariant assertions because they have the possibility of introducing false positives because of an incorrect code path. For example:

function invariant_example() external {
    if (protocolCondition) return;

    assertEq(val1, val2);
}

In this situation, if protocolCondition == true, the invariant is not asserted at all. Sometimes this can be desired behavior, but it can cause issues if the protocolCondition is true for the whole fuzzing campaign unexpectedly, or there is a logic error in the condition itself. For this reason its better to try and define an alternative invariant for that condition as well, for example:

function invariant_example() external {
    if (protocolCondition) {
        assertLe(val1, val2);
        return;
    };

    assertEq(val1, val2);
}

Another approach to handle different invariants across protocol states is to utilize dedicated invariant testing contracts for different scenarios. These scenarios can be bootstrapped using the setUp function, but it is more powerful to leverage invariant targets to govern the fuzzer to behave in a way that will only yield certain results (e.g., avoid liquidations).

Invariant Targets

Target Contracts: The set of contracts that will be called over the course of a given invariant test fuzzing campaign. This set of contracts defaults to all contracts that were deployed in the setUp function, but can be customized to allow for more advanced invariant testing.

Target Senders: The invariant test fuzzer picks values for msg.sender at random when performing fuzz campaigns to simulate multiple actors in a system by default. If desired, the set of senders can be customized in the setUp function.

Target Selectors: The set of function selectors that are used by the fuzzer for invariant testing. These can be used to use a subset of functions within a given target contract.

Target Artifacts: The desired ABI to be used for a given contract. These can be used for proxy contract configurations.

Target Artifact Selectors: The desired subset of function selectors to be used within a given ABI to be used for a given contract. These can be used for proxy contract configurations.

Priorities for the invariant fuzzer in the cases of target clashes are:

targetSelectors | targetArtifactSelectors > excludeContracts | excludeArtifacts > targetContracts | targetArtifacts

Function Call Probability Distribution

Functions from these contracts will be called at random with fuzzed inputs. The probability of a function being called is broken down by contract and then by function.

For example:

targetContract1: 50%
├─ function1: 50% (25%)
└─ function2: 50% (25%)

targetContract2: 50%
├─ function1: 25% (12.5%)
├─ function2: 25% (12.5%)
├─ function3: 25% (12.5%)
└─ function4: 25% (12.5%)

This is something to be mindful of when designing target contracts, as target contracts with less functions will have each function called more often due to this probability distribution.

Invariant Test Helper Functions

Invariant test helper functions are included in forge-std to allow for configurable invariant test setup. The helper functions are outlined below:

Function	Description
`excludeContract(address newExcludedContract_)`	Adds a given address to the `_excludedContracts` array. This set of contracts is explicitly excluded from the target contracts.
`excludeSender(address newExcludedSender_)`	Adds a given address to the `_excludedSenders` array. This set of addresses is explicitly excluded from the target senders.
`excludeArtifact(string memory newExcludedArtifact_)`	Adds a given string to the `_excludedArtifacts` array. This set of strings is explicitly excluded from the target artifacts.
`targetArtifact(string memory newTargetedArtifact_)`	Adds a given string to the `_targetedArtifacts` array. This set of strings is used for the target artifacts.
`targetArtifactSelector(FuzzSelector memory newTargetedArtifactSelector_)`	Adds a given `FuzzSelector` to the to `_targetedArtifactSelectors` array. This set of `FuzzSelector`s is used for the target artifact selectors.
`targetContract(address newTargetedContract_)`	Adds a given address to the to `_targetedContracts` array. This set of addresses is used for the target contracts. This array overwrites the set of contracts that was deployed during the `setUp`.
`targetSelector(FuzzSelector memory newTargetedSelector_)`	Adds a given `FuzzSelector` to the to `_targetedSelectors` array. This set of `FuzzSelector`s is used for the target contract selectors.
`targetSender(address newTargetedSender_)`	Adds a given address to the to `_targetedSenders` array. This set of addresses is used for the target senders.

Target Contract Setup

Target contracts can be set up using the following three methods:

Contracts that are manually added to the targetContracts array are added to the set of target contracts.
Contracts that are deployed in the setUp function are automatically added to the set of target contracts (only works if no contracts have been manually added using option 1).
Contracts that are deployed in the setUp can be removed from the target contracts if they are added to the excludeContracts array.

Open Testing

The default configuration for target contracts is set to all contracts that are deployed during the setup. For smaller modules and more arithmetic contracts, this works well. For example:

contract ExampleContract1 {

    uint256 public val1;
    uint256 public val2;
    uint256 public val3;

    function addToA(uint256 amount) external {
        val1 += amount;
        val3 += amount;
    }

    function addToB(uint256 amount) external {
        val2 += amount;
        val3 += amount;
    }

}

This contract could be deployed and tested using the default target contract pattern:

contract InvariantExample1 is Test {

    ExampleContract1 foo;

    function setUp() external {
        foo = new ExampleContract1();
    }

    function invariant_A() external {
        assertEq(foo.val1() + foo.val2(), foo.val3());
    }

    function invariant_B() external {
        assertGe(foo.val1() + foo.val2(), foo.val1());
    }

}

This setup will call foo.addToA() and foo.addToB() with a 50%-50% probability distribution with fuzzed inputs. Inevitably, the inputs will start to cause overflows and the function calls will start reverting. Since the default configuration in invariant testing is fail_on_revert = false, this will not cause the tests to fail. The invariants will hold throughout the rest of the fuzzing campaign and the result is that the test will pass. The output will look something like this:

[PASS] invariant_A() (runs: 50, calls: 10000, reverts: 5533)
[PASS] invariant_B() (runs: 50, calls: 10000, reverts: 5533)

Handler-Based Testing

For more complex and integrated protocols, more sophisticated target contract usage is required to achieve the desired results. To illustrate how Handlers can be leveraged, the following contract will be used (an ERC-4626 based contract that accepts deposits of another ERC-20 token):

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.17;

interface IERC20Like {

    function balanceOf(address owner_) external view returns (uint256 balance_);

    function transferFrom(
        address owner_,
        address recipient_,
        uint256 amount_
    ) external returns (bool success_);

}

contract Basic4626Deposit {

    /**********************************************************************************************/
    /*** Storage                                                                                ***/
    /**********************************************************************************************/

    address public immutable asset;

    string public name;
    string public symbol;

    uint8 public immutable decimals;

    uint256 public totalSupply;

    mapping(address => uint256) public balanceOf;

    /**********************************************************************************************/
    /*** Constructor                                                                            ***/
    /**********************************************************************************************/

    constructor(address asset_, string memory name_, string memory symbol_, uint8 decimals_) {
        asset    = asset_;
        name     = name_;
        symbol   = symbol_;
        decimals = decimals_;
    }

    /**********************************************************************************************/
    /*** External Functions                                                                     ***/
    /**********************************************************************************************/

    function deposit(uint256 assets_, address receiver_) external returns (uint256 shares_) {
        shares_ = convertToShares(assets_);

        require(receiver_ != address(0), "ZERO_RECEIVER");
        require(shares_   != uint256(0), "ZERO_SHARES");
        require(assets_   != uint256(0), "ZERO_ASSETS");

        totalSupply += shares_;

        // Cannot overflow because totalSupply would first overflow in the statement above.
        unchecked { balanceOf[receiver_] += shares_; }

        require(
            IERC20Like(asset).transferFrom(msg.sender, address(this), assets_),
            "TRANSFER_FROM"
        );
    }

    function transfer(address recipient_, uint256 amount_) external returns (bool success_) {
        balanceOf[msg.sender] -= amount_;

        // Cannot overflow because minting prevents overflow of totalSupply,
        // and sum of user balances == totalSupply.
        unchecked { balanceOf[recipient_] += amount_; }

        return true;
    }

    /**********************************************************************************************/
    /*** Public View Functions                                                                  ***/
    /**********************************************************************************************/

    function convertToShares(uint256 assets_) public view returns (uint256 shares_) {
        uint256 supply_ = totalSupply;  // Cache to stack.

        shares_ = supply_ == 0 ? assets_ : (assets_ * supply_) / totalAssets();
    }

    function totalAssets() public view returns (uint256 assets_) {
        assets_ = IERC20Like(asset).balanceOf(address(this));
    }

}

Handler Functions

This contract's deposit function requires that the caller has a non-zero balance of the ERC-20 asset. In the Open invariant testing approach, deposit() and transfer() would be called with a 50-50% distribution, but they would revert on every call. This would cause the invariant tests to "pass", but in reality no state was manipulated in the desired contract at all. This is where target contracts can be leveraged. When a contract requires some additional logic in order to function properly, it can be added in a dedicated contract called a Handler.

function deposit(uint256 assets) public virtual {
    asset.mint(address(this), assets);

    asset.approve(address(token), assets);

    uint256 shares = token.deposit(assets, address(this));
}

This contract will provide the necessary setup before a function call is made in order to ensure it is successful.

Building on this concept, Handlers can be used to develop more sophisticated invariant tests. With Open invariant testing, the tests run as shown in the diagram below, with random sequences of function calls being made to the protocol contracts directly with fuzzed parameters. This will cause reverts for more complex systems as outlined above.

Blank diagram

By manually adding all Handler contracts to the targetContracts array, all function calls made to protocol contracts can be made in a way that is governed by the Handler to ensure successful calls. This is outlined in the diagram below.

Invariant Diagrams - Page 2

With this layer between the fuzzer and the protocol, more powerful testing can be achieved.

Handler Ghost Variables

Within Handlers, "ghost variables" can be tracked across multiple function calls to add additional information for invariant tests. A good example of this is summing all of the shares that each LP owns after depositing into the ERC-4626 token as shown above, and using that in the invariant (totalSupply == sumBalanceOf).

function deposit(uint256 assets) public virtual {
    asset.mint(address(this), assets);

    asset.approve(address(token), assets);

    uint256 shares = token.deposit(assets, address(this));

    sumBalanceOf += shares;
}

Function-Level Assertions

Another benefit is the ability to perform assertions on function calls as they are happening. An example is asserting the ERC-20 balance of the LP has decremented by assets during the deposit function call, as well as their LP token balance incrementing by shares. In this way, handler functions are similar to fuzz tests because they can take in fuzzed inputs, perform state changes, and assert before/after state.

function deposit(uint256 assets) public virtual {
    asset.mint(address(this), assets);

    asset.approve(address(token), assets);

    uint256 beforeBalance = asset.balanceOf(address(this));

    uint256 shares = token.deposit(assets, address(this));

    assertEq(asset.balanceOf(address(this)), beforeBalance - assets);

    sumBalanceOf += shares;
}

Bounded/Unbounded Functions

In addition, with Handlers, input parameters can be bounded to reasonable expected values such that fail_on_revert in foundry.toml can be set to true. This can be accomplished using the bound() helper function from forge-std. This ensures that every function call that is being made by the fuzzer must be successful against the protocol in order to get tests to pass. This is very useful for visibility and confidence that the protocol is being tested in the desired way.

function deposit(uint256 assets) external {
    assets = bound(assets, 0, 1e30);

    asset.mint(address(this), assets);

    asset.approve(address(token), assets);

    uint256 beforeBalance = asset.balanceOf(address(this));

    uint256 shares = token.deposit(assets, address(this));

    assertEq(asset.balanceOf(address(this)), beforeBalance - assets);

    sumBalanceOf += shares;
}

This can also be accomplished by inheriting non-bounded functions from dedicated "unbounded" Handler contracts that can be used for fail_on_revert = false testing. This type of testing is also useful since it can expose issues in assumptions made with bound function usage.

// Unbounded
function deposit(uint256 assets) public virtual {
    asset.mint(address(this), assets);

    asset.approve(address(token), assets);

    uint256 beforeBalance = asset.balanceOf(address(this));

    uint256 shares = token.deposit(assets, address(this));

    assertEq(asset.balanceOf(address(this)), beforeBalance - assets);

    sumBalanceOf += shares;
}

// Bounded
function deposit(uint256 assets) external {
    assets = bound(assets, 0, 1e30);

    super.deposit(assets);
}

Actor Management

In the function calls above, it can be seen that address(this) is the sole depositor in the ERC-4626 contract, which is not a realistic representation of its intended use. By leveraging the prank cheatcodes in forge-std, each Handler can manage a set of actors and use them to perform the same function call from different msg.sender addresses. This can be accomplished using the following modifier:

address[] public actors;

address internal currentActor;

modifier useActor(uint256 actorIndexSeed) {
    currentActor = actors[bound(actorIndexSeed, 0, actors.length - 1)];
    vm.startPrank(currentActor);
    _;
    vm.stopPrank();
}

Using multiple actors allows for more granular ghost variable usage as well. This is demonstrated in the functions below:

// Unbounded
function deposit(
    uint256 assets,
    uint256 actorIndexSeed
) public virtual useActor(actorIndexSeed) {
    asset.mint(currentActor, assets);

    asset.approve(address(token), assets);

    uint256 beforeBalance = asset.balanceOf(address(this));

    uint256 shares = token.deposit(assets, address(this));

    assertEq(asset.balanceOf(address(this)), beforeBalance - assets);

    sumBalanceOf += shares;

    sumDeposits[currentActor] += assets
}

// Bounded
function deposit(uint256 assets, uint256 actorIndexSeed) external {
    assets = bound(assets, 0, 1e30);

    super.deposit(assets, actorIndexSeed);
}

Differential Testing

Forge can be used for differential testing and differential fuzzing. You can even test against non-EVM executables using the ffi cheatcode.

Background

Differential testing cross references multiple implementations of the same function by comparing each one's output. Imagine we have a function specification F(X), and two implementations of that specification: f1(X) and f2(X). We expect f1(x) == f2(x) for all x that exist in an appropriate input space. If f1(x) != f2(x), we know that at least one function is incorrectly implementing F(X). This process of testing for equality and identifying discrepancies is the core of differential testing.

Differential fuzzing is an extension of differential testing. Differential fuzzing programatically generates many values of x to find discrepancies and edge cases that manually chosen inputs might not reveal.

Note: the == operator in this case can be a custom definition of equality. For example, if testing floating point implementations, you might use approximate equality with a certain tolerance.

Some real life uses of this type of testing include:

Comparing upgraded implementations to their predecessors
Testing code against known reference implementations
Confirming compatibility with third party tools and dependencies

Below are some examples of how Forge is used for differential testing.

Primer: The `ffi` cheatcode

ffi allows you to execute an arbitrary shell command and capture the output. Here's a mock example:

import "forge-std/Test.sol";

contract TestContract is Test {

    function testMyFFI () public {
        string[] memory cmds = new string[](2);
        cmds[0] = "cat";
        cmds[1] = "address.txt"; // assume contains abi-encoded address.
        bytes memory result = vm.ffi(cmds);
        address loadedAddress = abi.decode(result, (address));
        // Do something with the address
        // ...
    }
}

An address has previously been written to address.txt, and we read it in using the FFI cheatcode. This data can now be used throughout your test contract.

Example: Differential Testing Merkle Tree Implementations

Merkle Trees are a cryptographic commitment scheme frequently used in blockchain applications. Their popularity has led to a number of different implementations of Merkle Tree generators, provers, and verifiers. Merkle roots and proofs are often generated using a language like JavaScript or Python, while proof verification usually occurs on-chain in Solidity.

Murky is a complete implementation of Merkle roots, proofs, and verification in Solidity. Its test suite includes differential tests against OpenZeppelin's Merkle proof library, as well as root generation tests against a reference JavaScript implementation. These tests are powered by Foundry's fuzzing and ffi capabilities.

Differential fuzzing against a reference TypeScript implementation

Using the ffi cheatcode, Murky tests its own Merkle root implementation against a TypeScript implementation using data provided by Forge's fuzzer:

function testMerkleRootMatchesJSImplementationFuzzed(bytes32[] memory leaves) public {
    vm.assume(leaves.length > 1);
    bytes memory packed = abi.encodePacked(leaves);
    string[] memory runJsInputs = new string[](8);

    // Build ffi command string
    runJsInputs[0] = 'npm';
    runJsInputs[1] = '--prefix';
    runJsInputs[2] = 'differential_testing/scripts/';
    runJsInputs[3] = '--silent';
    runJsInputs[4] = 'run';
    runJsInputs[5] = 'generate-root-cli';
    runJsInputs[6] = leaves.length.toString();
    runJsInputs[7] = packed.toHexString();

    // Run command and capture output
    bytes memory jsResult = vm.ffi(runJsInputs);
    bytes32 jsGeneratedRoot = abi.decode(jsResult, (bytes32));

    // Calculate root using Murky
    bytes32 murkyGeneratedRoot = m.getRoot(leaves);
    assertEq(murkyGeneratedRoot, jsGeneratedRoot);
}

Note: see Strings2.sol in the Murky Repo for the library that enables (bytes memory).toHexString()

Forge runs npm --prefix differential_testing/scripts/ --silent run generate-root-cli {numLeaves} {hexEncodedLeaves}. This calculates the Merkle root for the input data using the reference JavaScript implementation. The script prints the root to stdout, and that printout is captured as bytes in the return value of vm.ffi().

The test then calculates the root using the Solidity implementation.

Finally, the test asserts that the both roots are exactly equal. If they are not equal, the test fails.

Differential fuzzing against OpenZeppelin's Merkle Proof Library

You may want to use differential testing against another Solidity implementation. In that case, ffi is not needed. Instead, the reference implementation is imported directly into the test.

import "openzeppelin-contracts/contracts/utils/cryptography/MerkleProof.sol";
//...
function testCompatabilityOpenZeppelinProver(bytes32[] memory _data, uint256 node) public {
    vm.assume(_data.length > 1);
    vm.assume(node < _data.length);
    bytes32 root = m.getRoot(_data);
    bytes32[] memory proof = m.getProof(_data, node);
    bytes32 valueToProve = _data[node];
    bool murkyVerified = m.verifyProof(root, proof, valueToProve);
    bool ozVerified = MerkleProof.verify(proof, root, valueToProve);
    assertTrue(murkyVerified == ozVerified);
}

Differential testing against a known edge case

Differential tests are not always fuzzed -- they are also useful for testing known edge cases. In the case of the Murky codebase, the initial implementation of the log2ceil function did not work for certain arrays whose lengths were close to a power of 2 (like 129). As a safety check, a test is always run against an array of this length and compared to the TypeScript implementation. You can see the full test here.

Standardized Testing against reference data

FFI is also useful for injecting reproducible, standardized data into the testing environment. In the Murky library, this is used as a benchmark for gas snapshotting (see forge snapshot).

bytes32[100] data;
uint256[8] leaves = [4, 8, 15, 16, 23, 42, 69, 88];

function setUp() public {
    string[] memory inputs = new string[](2);
    inputs[0] = "cat";
    inputs[1] = "src/test/standard_data/StandardInput.txt";
    bytes memory result =  vm.ffi(inputs);
    data = abi.decode(result, (bytes32[100]));
    m = new Merkle();
}

function testMerkleGenerateProofStandard() public view {
    bytes32[] memory _data = _getData();
    for (uint i = 0; i < leaves.length; ++i) {
        m.getProof(_data, leaves[i]);
    }
}

src/test/standard_data/StandardInput.txt is a text file that contains an encoded bytes32[100] array. It's generated outside of the test and can be used in any language's Web3 SDK. It looks something like:

0xf910ccaa307836354233316666386231414464306335333243453944383735313..423532

The standardized testing contract reads in the file using ffi. It decodes the data into an array and then, in this example, generates proofs for 8 different leaves. Because the data is constant and standard, we can meaningfully measure gas and performance improvements using this test.

Of course, one could just hardcode the array into the test! But that makes it much harder to do consistent testing across contracts, implementations, etc.

Example: Differential Testing Gradual Dutch Auctions

The reference implementation for Paradigm's Gradual Dutch Auction mechanism contains a number of differential, fuzzed tests. It is an excellent repository to further explore differential testing using ffi.

Differential tests for Discrete GDAs
Differential tests for Continuous GDAs
Reference Python implementation

Reference Repositories

If you have another repository that would serve as a reference, please contribute it!

Deploying

Forge can deploy smart contracts to a given network with the forge create command.

Forge can deploy only one contract at a time.

To deploy a contract, you must provide a RPC URL (env: ETH_RPC_URL) and the private key of the account that will deploy the contract.

To deploy MyContract to a network:

$ forge create --rpc-url <your_rpc_url> --private-key <your_private_key> src/MyContract.sol:MyContract
compiling...
success.
Deployer: 0xa735b3c25f...
Deployed to: 0x4054415432...
Transaction hash: 0x6b4e0ff93a...

Solidity files may contain multiple contracts. :MyContract above specifies which contract to deploy from the src/MyContract.sol file.

Use the --constructor-args flag to pass arguments to the constructor:

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.0;

import {ERC20} from "solmate/tokens/ERC20.sol";

contract MyToken is ERC20 {
    constructor(
        string memory name,
        string memory symbol,
        uint8 decimals,
        uint256 initialSupply
    ) ERC20(name, symbol, decimals) {
        _mint(msg.sender, initialSupply);
    }
}

Additionally, we can tell Forge to verify our contract on Etherscan, Sourcify or Blockscout, if the network is supported, by passing --verify.

$ forge create --rpc-url <your_rpc_url> \
    --constructor-args "ForgeUSD" "FUSD" 18 1000000000000000000000 \
    --private-key <your_private_key> \
    --etherscan-api-key <your_etherscan_api_key> \
    --verify \
    src/MyToken.sol:MyToken

Verifying a pre-existing contract

It is recommended to use the --verify flag with forge create to automatically verify the contract on explorer after a deployment. Note that for Etherscan ETHERSCAN_API_KEY must be set.

If you are verifying an already deployed contract, read on.

You can verify a contract on Etherscan, Sourcify or Blockscout with the forge verify-contract command.

You must provide:

the contract address
the contract name or the path to the contract <path>:<contractname>
your Etherscan API key (env: ETHERSCAN_API_KEY) (if verifying on Etherscan).

Moreover, you may need to provide:

the constructor arguments in the ABI-encoded format, if there are any
compiler version used for build, with 8 hex digits from the commit version prefix (the commit will usually not be a nightly build). It is auto-detected if not specified.
the number of optimizations, if the Solidity optimizer was activated. It is auto-detected if not specified.
the chain ID, if the contract is not on Ethereum Mainnet

Let's say you want to verify MyToken (see above). You set the number of optimizations to 1 million, compiled it with v0.8.10, and deployed it, as shown above, to the Sepolia testnet (chain ID: 11155111). Note that --num-of-optimizations will default to 0 if not set on verification, while it defaults to 200 if not set on deployment, so make sure you pass --num-of-optimizations 200 if you left the default compilation settings.

Here's how to verify it:

forge verify-contract \
    --chain-id 11155111 \
    --num-of-optimizations 1000000 \
    --watch \
    --constructor-args $(cast abi-encode "constructor(string,string,uint256,uint256)" "ForgeUSD" "FUSD" 18 1000000000000000000000) \
    --etherscan-api-key <your_etherscan_api_key> \
    --compiler-version v0.8.10+commit.fc410830 \
    <the_contract_address> \
    src/MyToken.sol:MyToken 

Submitted contract for verification:
                Response: `OK`
                GUID: `a6yrbjp5prvakia6bqp5qdacczyfhkyi5j1r6qbds1js41ak1a`
                url: https://sepolia.etherscan.io//address/0x6a54…3a4c#code

It is recommended to use the --watch flag along with verify-contract command in order to poll for the verification result.

If the --watch flag was not supplied, you can check the verification status with the forge verify-check command:

$ forge verify-check --chain-id 11155111 <GUID> <your_etherscan_api_key>
Contract successfully verified.

💡 Tip

Use Cast's abi-encode to ABI-encode arguments.

In this example, we ran cast abi-encode "constructor(string,string,uint8,uint256)" "ForgeUSD" "FUSD" 18 1000000000000000000000 to ABI-encode the arguments.

Troubleshooting

`Invalid character 'x' at position 1`

Make sure the private key string does not begin with 0x.

`EIP-1559 not activated`

EIP-1559 is not supported or not activated on the RPC server. Pass the --legacy flag to use legacy transactions instead of the EIP-1559 ones. If you do development in a local environment, you can use Hardhat instead of Ganache.

`Failed to parse tokens`

Make sure the passed arguments are of correct type.

`Signature error`

Make sure the private key is correct.

`Compiler version commit for verify`

If you want to check the exact commit you are running locally, try: ~/.svm/0.x.y/solc-0.x.y --version where x and y are major and minor version numbers respectively. The output of this will be something like:

solc, the solidity compiler commandline interface
Version: 0.8.12+commit.f00d7308.Darwin.appleclang

Note: You cannot just paste the entire string "0.8.12+commit.f00d7308.Darwin.appleclang" as the argument for the compiler-version. But you can use the 8 hex digits of the commit to look up exactly what you should copy and paste from compiler version.

Known Issues

Verifying Contracts With Ambiguous Import Paths

Forge passes source directories (src, lib, test etc) as --include-path arguments to the compiler. This means that given the following project tree

|- src
|-- folder
|--- Contract.sol
|--- IContract.sol

it is possible to import IContract inside the Contract.sol using folder/IContract.sol import path.

Etherscan is not able to recompile such sources. Consider changing the imports to use relative import path.

Verifying Contracts With No Bytecode Hash

Currently, it's not possible to verify contracts on Etherscan with bytecode_hash set to none. Click here to learn more about how metadata hash is used for source code verification.

Gas Tracking

Forge can help you estimate how much gas your contract will consume.

Currently, Forge ships with two different tools for this job, but they may be merged in the future:

Gas reports: Gas reports give you an overview of how much Forge thinks the individual functions in your contracts will consume in gas.
Gas snapshots: Gas snapshots give you an overview of how much each test consumes in gas.

Gas reports and gas snapshots differ in some ways:

Gas reports use tracing to figure out gas costs for individual contract calls.
This gives more granular insight, at the cost of speed.
Gas snapshots have more built-in tools, such as diffs and exporting the results to a file.
Snapshots are not as granular as gas reports, but they are faster to generate.

Gas Reports

Forge can produce gas reports for your contracts. You can configure which contracts output gas reports via the gas_reports field in foundry.toml.

To produce reports for specific contracts:

gas_reports = ["MyContract", "MyContractFactory"]

To produce reports for all contracts:

gas_reports = ["*"]

To generate gas reports, run forge test --gas-report.

You can also use it in combination with other subcommands, such as forge test --match-test testBurn --gas-report, to generate only a gas report relevant to this test.

Example output:

╭───────────────────────┬─────────────────┬────────┬────────┬────────┬─────────╮
│ MockERC1155 contract  ┆                 ┆        ┆        ┆        ┆         │
╞═══════════════════════╪═════════════════╪════════╪════════╪════════╪═════════╡
│ Deployment Cost       ┆ Deployment Size ┆        ┆        ┆        ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 1082720               ┆ 5440            ┆        ┆        ┆        ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name         ┆ min             ┆ avg    ┆ median ┆ max    ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ balanceOf             ┆ 596             ┆ 596    ┆ 596    ┆ 596    ┆ 44      │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ balanceOfBatch        ┆ 2363            ┆ 4005   ┆ 4005   ┆ 5647   ┆ 2       │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ batchBurn             ┆ 2126            ┆ 5560   ┆ 2584   ┆ 11970  ┆ 3       │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ batchMint             ┆ 2444            ┆ 135299 ┆ 125081 ┆ 438531 ┆ 18      │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ burn                  ┆ 814             ┆ 2117   ┆ 2117   ┆ 3421   ┆ 2       │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ isApprovedForAll      ┆ 749             ┆ 749    ┆ 749    ┆ 749    ┆ 1       │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ mint                  ┆ 26039           ┆ 31943  ┆ 27685  ┆ 118859 ┆ 22      │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ safeBatchTransferFrom ┆ 2561            ┆ 137750 ┆ 126910 ┆ 461304 ┆ 8       │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ safeTransferFrom      ┆ 1335            ┆ 34505  ┆ 28103  ┆ 139557 ┆ 9       │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ setApprovalForAll     ┆ 24485           ┆ 24485  ┆ 24485  ┆ 24485  ┆ 12      │
╰───────────────────────┴─────────────────┴────────┴────────┴────────┴─────────╯

╭───────────────────────┬─────────────────┬────────┬────────┬────────┬─────────╮
│ Example contract      ┆                 ┆        ┆        ┆        ┆         │
╞═══════════════════════╪═════════════════╪════════╪════════╪════════╪═════════╡
│ Deployment Cost       ┆ Deployment Size ┆        ┆        ┆        ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 1082720               ┆ 5440            ┆        ┆        ┆        ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name         ┆ min             ┆ avg    ┆ median ┆ max    ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ foo                   ┆ 596             ┆ 596    ┆ 596    ┆ 596    ┆ 44      │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ bar                   ┆ 2363            ┆ 4005   ┆ 4005   ┆ 5647   ┆ 2       │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ baz                   ┆ 2126            ┆ 5560   ┆ 2584   ┆ 11970  ┆ 3       │
╰───────────────────────┴─────────────────┴────────┴────────┴────────┴─────────╯

You can also ignore contracts via the gas_reports_ignore field in foundry.toml:

gas_reports_ignore = ["Example"]

This would change the output to:

╭───────────────────────┬─────────────────┬────────┬────────┬────────┬─────────╮
│ MockERC1155 contract  ┆                 ┆        ┆        ┆        ┆         │
╞═══════════════════════╪═════════════════╪════════╪════════╪════════╪═════════╡
│ Deployment Cost       ┆ Deployment Size ┆        ┆        ┆        ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ 1082720               ┆ 5440            ┆        ┆        ┆        ┆         │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ Function Name         ┆ min             ┆ avg    ┆ median ┆ max    ┆ # calls │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ balanceOf             ┆ 596             ┆ 596    ┆ 596    ┆ 596    ┆ 44      │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ balanceOfBatch        ┆ 2363            ┆ 4005   ┆ 4005   ┆ 5647   ┆ 2       │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ batchBurn             ┆ 2126            ┆ 5560   ┆ 2584   ┆ 11970  ┆ 3       │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ batchMint             ┆ 2444            ┆ 135299 ┆ 125081 ┆ 438531 ┆ 18      │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ burn                  ┆ 814             ┆ 2117   ┆ 2117   ┆ 3421   ┆ 2       │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ isApprovedForAll      ┆ 749             ┆ 749    ┆ 749    ┆ 749    ┆ 1       │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ mint                  ┆ 26039           ┆ 31943  ┆ 27685  ┆ 118859 ┆ 22      │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ safeBatchTransferFrom ┆ 2561            ┆ 137750 ┆ 126910 ┆ 461304 ┆ 8       │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ safeTransferFrom      ┆ 1335            ┆ 34505  ┆ 28103  ┆ 139557 ┆ 9       │
├╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┤
│ setApprovalForAll     ┆ 24485           ┆ 24485  ┆ 24485  ┆ 24485  ┆ 12      │
╰───────────────────────┴─────────────────┴────────┴────────┴────────┴─────────╯

Gas Snapshots

Forge can generate gas snapshots for all your test functions. This can be useful to get a general feel for how much gas your contract will consume, or to compare gas usage before and after various optimizations.

To generate the gas snapshot, run forge snapshot.

This will generate a file called .gas-snapshot by default with all your tests and their respective gas usage.

$ forge snapshot
$ cat .gas-snapshot

ERC20Test:testApprove() (gas: 31162)
ERC20Test:testBurn() (gas: 59875)
ERC20Test:testFailTransferFromInsufficientAllowance() (gas: 81034)
ERC20Test:testFailTransferFromInsufficientBalance() (gas: 81662)
ERC20Test:testFailTransferInsufficientBalance() (gas: 52882)
ERC20Test:testInfiniteApproveTransferFrom() (gas: 90167)
ERC20Test:testMetadata() (gas: 14606)
ERC20Test:testMint() (gas: 53830)
ERC20Test:testTransfer() (gas: 60473)
ERC20Test:testTransferFrom() (gas: 84152)

Filtering

If you would like to specify a different output file, run forge snapshot --snap <FILE_NAME>.

You can also sort the results by gas usage. Use the --asc option to sort the results in ascending order and --desc to sort the results in descending order.

Finally, you can also specify a min/max gas threshold for all your tests. To only include results above a threshold, you can use the --min <VALUE> option. In the same way, to only include results under a threshold, you can use the --max <VALUE> option.

Keep in mind that the changes will be made in the snapshot file, and not in the snapshot being displayed on your screen.

You can also use it in combination with the filters for forge test, such as forge snapshot --match-path contracts/test/ERC721.t.sol to generate a gas snapshot relevant to this test contract.

Comparing gas usage

If you would like to compare the current snapshot file with your latest changes, you can use the --diff or --check options.

--diff will compare against the snapshot and display changes from the snapshot.

It can also optionally take a file name (--diff <FILE_NAME>), with the default being .gas-snapshot.

For example:

$ forge snapshot --diff .gas-snapshot2

Running 10 tests for src/test/ERC20.t.sol:ERC20Test
[PASS] testApprove() (gas: 31162)
[PASS] testBurn() (gas: 59875)
[PASS] testFailTransferFromInsufficientAllowance() (gas: 81034)
[PASS] testFailTransferFromInsufficientBalance() (gas: 81662)
[PASS] testFailTransferInsufficientBalance() (gas: 52882)
[PASS] testInfiniteApproveTransferFrom() (gas: 90167)
[PASS] testMetadata() (gas: 14606)
[PASS] testMint() (gas: 53830)
[PASS] testTransfer() (gas: 60473)
[PASS] testTransferFrom() (gas: 84152)
Test result: ok. 10 passed; 0 failed; finished in 2.86ms
testBurn() (gas: 0 (0.000%))
testFailTransferFromInsufficientAllowance() (gas: 0 (0.000%))
testFailTransferFromInsufficientBalance() (gas: 0 (0.000%))
testFailTransferInsufficientBalance() (gas: 0 (0.000%))
testInfiniteApproveTransferFrom() (gas: 0 (0.000%))
testMetadata() (gas: 0 (0.000%))
testMint() (gas: 0 (0.000%))
testTransfer() (gas: 0 (0.000%))
testTransferFrom() (gas: 0 (0.000%))
testApprove() (gas: -8 (-0.000%))
Overall gas change: -8 (-0.000%)

--check will compare a snapshot with an existing snapshot file and display all the differences, if any. You can change the file to compare against by providing a different file name: --check <FILE_NAME>.

For example:

$ forge snapshot --check .gas-snapshot2

Running 10 tests for src/test/ERC20.t.sol:ERC20Test
[PASS] testApprove() (gas: 31162)
[PASS] testBurn() (gas: 59875)
[PASS] testFailTransferFromInsufficientAllowance() (gas: 81034)
[PASS] testFailTransferFromInsufficientBalance() (gas: 81662)
[PASS] testFailTransferInsufficientBalance() (gas: 52882)
[PASS] testInfiniteApproveTransferFrom() (gas: 90167)
[PASS] testMetadata() (gas: 14606)
[PASS] testMint() (gas: 53830)
[PASS] testTransfer() (gas: 60473)
[PASS] testTransferFrom() (gas: 84152)
Test result: ok. 10 passed; 0 failed; finished in 2.47ms
Diff in "ERC20Test::testApprove()": consumed "(gas: 31162)" gas, expected "(gas: 31170)" gas

Debugger

Forge ships with an interactive debugger.

The debugger is accessible on forge debug and on forge test.

Using forge test:

$ forge test --debug $FUNC

Where $FUNC is the signature of the function you want to debug. For example:

$ forge test --debug "testSomething()"

If you have multiple contracts with the same function name, you need to limit the matching functions down to only one case using --match-path and --match-contract.

If the matching test is a fuzz test, the debugger will open the first failing fuzz scenario, or the last successful one, whichever comes first.

Using forge debug:

$ forge debug --debug $FILE --sig $FUNC

Where $FILE is the path to the contract you want to debug, and $FUNC is the signature of the function you want to debug. For example:

$ forge debug --debug src/SomeContract.sol --sig "myFunc(uint256,string)" 123 "hello"

You can also specify raw calldata using --sig instead of a function signature.

If your source file contains more than one contract, specify the contract you want to debug using the --target-contract flag.

Debugger layout

An image of the debugger UI

When the debugger is run, you are presented with a terminal divided into four quadrants:

Quadrant 1: The opcodes in the debugging session, with the current opcode highlighted. Additionally, the address of the current account, the program counter and the accumulated gas usage is also displayed
Quadrant 2: The current stack, as well as the size of the stack
Quadrant 3: The source view
Quadrant 4: The current memory of the EVM

As you step through your code, you will notice that the words in the stack and memory sometimes change color.

For the memory:

Red words are about to be written to by the current opcode
Green words were written to by the previous opcode
Cyan words are being read by the current opcode

For the stack, cyan words are either being read or popped by the current opcode.

Navigating

General

q: Quit the debugger
h: Show help

Navigating calls

0-9 + k: Step a number of times backwards (alternatively scroll up with your mouse)
0-9 + j: Step a number of times forwards (alternatively scroll down with your mouse)
g: Move to the beginning of the transaction
G: Move to the end of the transaction
c: Move to the previous call-type instruction (i.e. CALL, STATICCALL, DELEGATECALL, and CALLCODE).
C: Move to the next call-type instruction
a: Move to the previous JUMP or JUMPI instruction
s: Move to the next JUMPDEST instruction
' + a-z: Move to <char> breakpoint set by a vm.breakpoint cheatcode

Navigating memory

Ctrl + j: Scroll the memory view down
Ctrl + k: Scroll the memory view up
m: Show memory as UTF8

Navigating the stack

J: Scroll the stack view down
K: Scroll the stack view up
t: Show labels on the stack to see what items the current op will consume

Overview of Cast

Cast is Foundry's command-line tool for performing Ethereum RPC calls. You can make smart contract calls, send transactions, or retrieve any type of chain data - all from your command-line!

How to use Cast

To use Cast, run the cast command followed by a subcommand:

$ cast <subcommand>

Examples

Let's use cast to retrieve the total supply of the DAI token:

$ cast call 0x6b175474e89094c44da98b954eedeac495271d0f "totalSupply()(uint256)" --rpc-url https://eth-mainnet.alchemyapi.io/v2/Lc7oIGYeL_QvInzI0Wiu_pOZZDEKBrdf
8603853182003814300330472690

cast also provides many convenient subcommands, such as for decoding calldata:

$ cast 4byte-decode 0x1F1F897F676d00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000003e7
1) "fulfillRandomness(bytes32,uint256)"
0x676d000000000000000000000000000000000000000000000000000000000000
999

You can also use cast to send arbitrary messages. Here's an example of sending a message between two Anvil accounts.

$ cast send --private-key <Your Private Key> 0x3c44cdddb6a900fa2b585dd299e03d12fa4293bc $(cast --from-utf8 "hello world") --rpc-url http://127.0.0.1:8545/

📚 Reference

See the cast Reference for a complete overview of all the available subcommands.

Overview of Anvil

Anvil is a local testnet node shipped with Foundry. You can use it for testing your contracts from frontends or for interacting over RPC.

Anvil is part of the Foundry suite and is installed alongside forge, cast, and chisel. If you haven't installed Foundry yet, see Foundry installation.

Note: If you have an older version of Foundry installed, you'll need to re-install foundryup in order for Anvil to be downloaded.

How to use Anvil

To use Anvil, simply type anvil. You should see a list of accounts and private keys available for use, as well as the address and port that the node is listening on.

Anvil is highly configurable. You can run anvil -h to see all the configuration options.

Some basic options are:

#  Number of dev accounts to generate and configure. [default: 10]
anvil -a, --accounts <ACCOUNTS>

# The EVM hardfork to use. [default: latest]
anvil --hardfork <HARDFORK>

# Port number to listen on. [default: 8545]
anvil  -p, --port <PORT>

📚 Reference

See the anvil Reference for in depth information on Anvil and its capabilities.

Overview of Chisel

Chisel is an advanced Solidity REPL shipped with Foundry. It can be used to quickly test the behavior of Solidity snippets on a local or forked network.

Chisel is part of the Foundry suite and is installed alongside forge, cast, and anvil. If you haven't installed Foundry yet, see Foundry installation.

Note: If you have an older version of Foundry installed, you'll need to re-install foundryup in order for Chisel to be downloaded.

How to use Chisel

To use Chisel, simply type chisel. From there, start writing Solidity code! Chisel will offer verbose feedback on each input.

Chisel can be used both within and outside of a foundry project. If the binary is executed in a Foundry project root, Chisel will inherit the project's configuration options.

To see available commands, type !help within the REPL.

📚 Reference

See the chisel Reference for in depth information on Chisel and its capabilities.

Configuring with `foundry.toml`

Forge can be configured using a configuration file called foundry.toml, which is placed in the root of your project.

Configuration can be namespaced by profiles. The default profile is named default, from which all other profiles inherit. You are free to customize the default profile, and add as many new profiles as you need.

Additionally, you can create a global foundry.toml in your home directory.

Let's take a look at a configuration file that contains two profiles: the default profile, which always enables the optimizer, as well as a CI profile, that always displays traces:

[profile.default]
optimizer = true
optimizer_runs = 20_000

[profile.ci]
verbosity = 4

When running forge, you can specify the profile to use using the FOUNDRY_PROFILE environment variable.

Standalone sections

Besides the profile sections, the configuration file can also contain standalone sections ([fmt], [fuzz], [invariant] etc). By default, each standalone section belongs to the default profile. i.e. [fmt] is equivalent to [profile.default.fmt].

To configure the standalone section for different profiles other than default, use syntax [profile.<profile name>.<standalone>]. i.e. [profile.ci.fuzz].

📚 Reference

See the foundry.toml Reference for a complete overview of what you can configure.

Continuous Integration

GitHub Actions

To test your project using GitHub Actions, here is a sample workflow:

on: [push]

name: test

jobs:
  check:
    name: Foundry project
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
        with:
          submodules: recursive

      - name: Install Foundry
        uses: foundry-rs/foundry-toolchain@v1
        with:
          version: nightly

      - name: Run tests
        run: forge test -vvv

Travis CI

To test your project using Travis CI, here is a sample workflow:

language: rust
cache:
  cargo: true
  directories:
    - $HOME/.foundry

install:
  - curl -L https://foundry.paradigm.xyz | bash
  - export PATH=$PATH:$HOME/.foundry/bin
  - foundryup -b master

script:
  - forge test -vvv

GitLab CI

To test your project using GitLab CI, here is a sample workflow: Note: check out Policy to fetch the remote image

variables:
  GIT_SUBMODULE_STRATEGY: recursive

jobs:
  image: ghcr.io/foundry-rs/foundry
  script:
    - forge install
    - forge test -vvv

Integrating with VSCode

You can get Solidity support for Visual Studio Code by installing the VSCode Solidity extension.

To make the extension play nicely with Foundry, you may have to tweak a couple of things.

1. Remappings

You may want to place your remappings in remappings.txt.

If they are already in foundry.toml, copy them over and use remappings.txt instead. If you just use the autogenerated remappings that Foundry provides, run forge remappings > remappings.txt.

2. Dependencies

You may have to add the following to your .vscode/settings.json for the extension to find your dependencies:

{
  "solidity.packageDefaultDependenciesContractsDirectory": "src",
  "solidity.packageDefaultDependenciesDirectory": "lib"
}

Where src is the source code directory and lib is your dependency directory.

3. Formatter

To enable the built-in formatter that comes with Foundry to automatically format your code on save, you can add the following settings to your .vscode/settings.json:

{
  "editor.formatOnSave": true,
  "[solidity]": {
    "editor.defaultFormatter": "JuanBlanco.solidity" 
  },
  "solidity.formatter": "forge",
}

To configure the formatter settings, refer to the Formatter reference.

4. Solc Version

Finally, it is recommended to specify a Solidity compiler version:

"solidity.compileUsingRemoteVersion": "v0.8.17"

To get Foundry in line with the chosen version, add the following to your default profile in foundry.toml.

solc = "0.8.17"

Shell Autocompletion

You can generate autocompletion shell scripts for bash, elvish, fish, powershell, and zsh.

zsh

First, ensure that the following is present somewhere in your ~/.zshrc file (if not, add it):

autoload -U compinit
compinit -i

Then run:

forge completions zsh > /usr/local/share/zsh/site-functions/_forge
cast completions zsh > /usr/local/share/zsh/site-functions/_cast
anvil completions zsh > /usr/local/share/zsh/site-functions/_anvil

For ARM-based systems:

forge completions zsh > /opt/homebrew/completions/zsh/_forge
cast completions zsh > /opt/homebrew/completions/zsh/_cast
anvil completions zsh > /opt/homebrew/completions/zsh/_anvil

fish

mkdir -p $HOME/.config/fish/completions
forge completions fish > $HOME/.config/fish/completions/forge.fish
cast completions fish > $HOME/.config/fish/completions/cast.fish
anvil completions fish > $HOME/.config/fish/completions/anvil.fish
source $HOME/.config/fish/config.fish

bash

mkdir -p $HOME/.local/share/bash-completion/completions
forge completions bash > $HOME/.local/share/bash-completion/completions/forge
cast completions bash > $HOME/.local/share/bash-completion/completions/cast
anvil completions bash > $HOME/.local/share/bash-completion/completions/anvil
exec bash

Static Analyzers

Slither

To test your project using slither, here is a sample slither.config.json:

{
  "filter_paths": "lib"
}

To run Slither on the entire project, you can use this command:

slither .

You do not need to provide remappings via the solc_remaps option as Slither will automatically detect remappings in a Foundry project. Slither will invoke forge to perform the build.

However, if you want to analyze a specific .sol file, then you do need to provide remappings:

{
  "solc_remaps": [
    "ds-test/=lib/ds-test/src/",
    "forge-std/=lib/forge-std/src/"
  ]
}

And you also need to update the solc compiler used by Slither to the same version used by Forge with solc-select:

pip3 install slither-analyzer
pip3 install solc-select
solc-select install 0.8.13
solc-select use 0.8.13
slither .

See the Slither wiki for more information.

In order to use a custom configuration, such as the sample slither.config.json mentioned above, the following command is used as mentioned in the slither-wiki. By default slither looks for the slither.config.json but you can define the path and any other json file of your choice:

slither --config-file <path>/file.config.json .

Example output (Raw):

Pragma version^0.8.13 (Counter.sol#2) necessitates a version too recent to be trusted. Consider deploying with 0.6.12/0.7.6/0.8.7
solc-0.8.13 is not recommended for deployment
Reference: https://github.com/crytic/slither/wiki/Detector-Documentation#incorrect-versions-of-solidity

setNumber(uint256) should be declared external:
        - Counter.setNumber(uint256) (Counter.sol#7-9)
increment() should be declared external:
        - Counter.increment() (Counter.sol#11-13)
Reference: https://github.com/crytic/slither/wiki/Detector-Documentation#public-function-that-could-be-declared-external
Counter.sol analyzed (1 contracts with 78 detectors), 4 result(s) found

Slither also has a GitHub Action for CI/CD.

Mythril

To test your project using mythril, here is a sample mythril.config.json:

{
  "remappings": [
    "ds-test/=lib/ds-test/src/",
    "forge-std/=lib/forge-std/src/"
  ],
  "optimizer": {
    "enabled": true,
    "runs": 200
  }
}

Note, you need switch rustc to nightly to install mythril:

rustup default nightly
pip3 install mythril
myth analyze src/Contract.sol --solc-json mythril.config.json

See the mythril docs for more information.

You can pass custom Solc compiler output to Mythril using the --solc-json flag. For example:

$ myth analyze src/Counter.sol --solc-json mythril.config.json
.
.
mythril.laser.plugin.loader [INFO]: Loading laser plugin: coverage
mythril.laser.plugin.loader [INFO]: Loading laser plugin: mutation-pruner
.
.
Achieved 11.56% coverage for code: 608060405234801561001057600080fd5b5060f78061001f6000396000f3fe6080604052348015600f57600080fd5b5060043610603c5760003560e01c80633fb5c1cb1460415780638381f58a146053578063d09de08a14606d575b600080fd5b6051604c3660046083565b600055565b005b605b60005481565b60405190815260200160405180910390f35b6051600080549080607c83609b565b9190505550565b600060208284031215609457600080fd5b5035919050565b60006001820160ba57634e487b7160e01b600052601160045260246000fd5b506001019056fea2646970667358221220659fce8aadca285da9206b61f95de294d3958c409cc3011ded856f421885867464736f6c63430008100033
mythril.laser.plugin.plugins.coverage.coverage_plugin [INFO]: Achieved 90.13% coverage for code: 6080604052348015600f57600080fd5b5060043610603c5760003560e01c80633fb5c1cb1460415780638381f58a146053578063d09de08a14606d575b600080fd5b6051604c3660046083565b600055565b005b605b60005481565b60405190815260200160405180910390f35b6051600080549080607c83609b565b9190505550565b600060208284031215609457600080fd5b5035919050565b60006001820160ba57634e487b7160e01b600052601160045260246000fd5b506001019056fea2646970667358221220659fce8aadca285da9206b61f95de294d3958c409cc3011ded856f421885867464736f6c63430008100033
mythril.laser.plugin.plugins.instruction_profiler [INFO]: Total: 1.0892839431762695 s
[ADD         ]   0.9974 %,  nr      9,  total   0.0109 s,  avg   0.0012 s,  min   0.0011 s,  max   0.0013 s
.
.
[SWAP1       ]   1.8446 %,  nr     18,  total   0.0201 s,  avg   0.0011 s,  min   0.0010 s,  max   0.0013 s
[SWAP2       ]   0.8858 %,  nr      9,  total   0.0096 s,  avg   0.0011 s,  min   0.0010 s,  max   0.0011 s

mythril.analysis.security [INFO]: Starting analysis
mythril.mythril.mythril_analyzer [INFO]: Solver statistics: 
Query count: 61 
Solver time: 3.6820807456970215
The analysis was completed successfully. No issues were detected.

The findings will be listed at the end of this output if any. Since the default Counter.sol doesn't have any logic, mythx reports that no issues were found.

Integrating with Hardhat

It's possible to have your Foundry project work alongside Hardhat. This assumes that you have a working Foundry project and want to add Hardhat. It also assumes familiarity with Hardhat.

Why does this not work out of the box?

Hardhat by default expects libraries to be installed in node_modules, the default folder for all NodeJS dependencies. Foundry expects them to be in lib. Of course we can configure Foundry but not easily to the directory structure of node_modules.

For this reason, the recommended setup is to use hardhat-preprocessor. Hardhat-preprocessor is, as the name suggests, a Hardhat plugin which allows us to preprocess our contracts before they are run through the Solidity compiler.

We use this to modify the import directives in our Solidity files to resolve absolute paths to the libraries based on the Foundry remappings.txt file before Hardhat attempts to compile them. This of course just happens in memory so your actual Solidity files are never changed. Now, Hardhat is happy to comply and compiles using the libraries you installed with Foundry.

Just show me the example repo!

Enjoy!

If you want to adapt this to a Foundry project you already have or learn how it works, read below:

Instructions

Inside your Foundry project working directory:

npm init - Setup your project details as usual.
npm install --save-dev hardhat - Install Hardhat.
npx hardhat - Setup your Hardhat project as you see fit in the same directory.
forge remappings > remappings.txt - You will need to re-run this every time you modify libraries in Foundry.

Now you need to make the following changes to your Hardhat project. The following assumes a TypeScript setup:

npm install --save-dev hardhat-preprocessor - Details on hardhat-preprocessor
Add import "hardhat-preprocessor"; to your hardhat.config.ts file.
Ensure the following function is present (you can add it to your hardhat.config.ts file or somewhere else and import it - also ensure import fs from "fs"; is present in the file it is added):

function getRemappings() {
  return fs
    .readFileSync("remappings.txt", "utf8")
    .split("\n")
    .filter(Boolean) // remove empty lines
    .map((line) => line.trim().split("="));
}

Thanks to @DrakeEvansV1 and @colinnielsen for this snippet

Add the following to your exported HardhatUserConfig object:

...
preprocess: {
  eachLine: (hre) => ({
    transform: (line: string) => {
      if (line.match(/^\s*import /i)) {
        for (const [from, to] of getRemappings()) {
          if (line.includes(from)) {
            line = line.replace(from, to);
            break;
          }
        }
      }
      return line;
    },
  }),
},
paths: {
  sources: "./src",
  cache: "./cache_hardhat",
},
...

Now, Hardhat should work well with Foundry. You can run Foundry tests or Hardhat tests / scripts and have access to your contracts.

Use Foundry in an existing Hardhat project

Suppose that you already have a Hardhat project with some dependencies such as @OpenZeppelin/contracts in directory node_modules/.

You can use Foundry test in this project in 4 steps.

Before we start, let's take a look at the directories:

Contracts are in contracts
Hardhat unit test is in test, and we will put Foundry test files in test/foundry
Hardhat puts its cache in cache, and we will put Foundry cache in forge-cache

4 steps to add Foundry test

Copy lib/forge-std from a newly-created empty Foundry project to this Hardhat project directory. A note: you can also run forge init --force to init a Foundry project in this non-empty directory and remove unneeded directories created by Foundry init.
Copy foundry.toml configuration to this Hardhat project directory and change src, out, test, cache_path in it:

[profile.default]
src = 'contracts'
out = 'out'
libs = ['node_modules', 'lib']
test = 'test/foundry'
cache_path  = 'forge-cache'

# See more config options https://book.getfoundry.sh/reference/config.html

Create a remappings.txt to make Foundry project work well with VS Code Solidity extension:

ds-test/=lib/forge-std/lib/ds-test/src/
forge-std/=lib/forge-std/src/

See more on remappings.txt and VS Code Solidity extension: Remapping dependencies, Integrating with VSCode

Make a sub-directory test/foundry and write Foundry tests in it.

Let's put the sample test file Contract.t.sol in this directory and run Foundry test

forge test

Now, Foundry test works in this existing Hardhat project. As the Hardhat project is not touched and it can work as before.

Best Practices

This guide documents the suggested best practices when developing with Foundry. In general, it's recommended to handle as much as possible with forge fmt, and anything this doesn't handle is below.

General Contract Guidance

Always use named import syntax, don't import full files. This restricts what is being imported to just the named items, not everything in the file. Importing full files can result in solc complaining about duplicate definitions and slither erroring, especially as repos grow and have more dependencies with overlapping names.
- Good: import {MyContract} from "src/MyContract.sol" to only import MyContract.
- Bad: import "src/MyContract.sol" imports everything in MyContract.sol. (Importing forge-std/Test or Script can be an exception here, so you get the console library, etc).
Sort imports by forge-std/ first, then dependencies, test/, script/, and finally src/. Within each, sort alphabetically by path (not by the explicit named items being imported). (Note: This may be removed once foundry-rs/foundry#3396 is merged).
Similarly, sort named imports. (Note: This may be removed once foundry-rs/foundry#3396 is resolved).
- Good: import {bar, foo} from "src/MyContract.sol"
- Bad: import {foo, bar} from "src/MyContract.sol"
Note the tradeoffs between absolute and relative paths for imports (where absolute paths are relative to the repo root, e.g. "src/interfaces/IERC20.sol"), and choose the best approach for your project:
- Absolute paths make it easier to see where files are from and reduce churn when moving files around.
- Relative paths make it more likely your editor can provide features like linting and autocomplete, since editors/extensions may not understand your remappings.
If copying a library from a dependency (instead of importing it), use the ignore = [] option in the config file to avoid formatting that file. This makes diffing it against the original simpler for reviewers and auditors.
Similarly, feel free to use the // forgefmt: disable-* comment directives to ignore lines/sections of code that look better with manual formatting. Supported values for * are:
- disable-line
- disable-next-line
- disable-next-item
- disable-start
- disable-end

Additional best practices from samsczun's How Do You Even Write Secure Code Anyways talk:

Use descriptive variable names.
Limit the number of active variables.
No redundant logic.
Early exit as much as possible to reduce mental load when seeing the code.
Related code should be placed near each other.
Delete unused code.

Tests

General Test Guidance

For testing MyContract.sol, the test file should be MyContract.t.sol. For testing MyScript.s.sol, the test file should be MyScript.t.sol.
- If the contract is big and you want to split it over multiple files, group them logically like MyContract.owner.t.sol, MyContract.deposits.t.sol, etc.
Never make assertions in the setUp function, instead use a dedicated test like test_SetUpState() if you need to ensure your setUp function does what you expected. More info on why in foundry-rs/foundry#1291
For unit tests, there are two major ways to organize the tests:
1. Treat contracts as describe blocks:
  - contract Add holds all unit tests for the add method of MyContract.
  - contract Supply holds all tests for the supply method.
  - contract Constructor hold all tests for the constructor.
  - A benefit of this approach is that smaller contracts should compile faster than large ones, so this approach of many small contracts should save time as test suites get large.
2. Have a Test contract per contract-under-test, with as many utilities and fixtures as you want:
  - contract MyContractTest holds all unit tests for MyContract.
  - function test_add_AddsTwoNumbers() lives within MyContractTest to test the add method.
  - function test_supply_UsersCanSupplyTokens() also lives within MyContractTest to test the supply method.
  - A benefit of this approach is that test output is grouped by contract-under-test, which makes it easier to quickly see where failures are.
Some general guidance for all tests:
- Test contracts/functions should be written in the same order as the original functions in the contract-under-test.
- All unit tests that test the same function should live serially in the test file.
- Test contracts can inherit from any helper contracts you want. For example contract MyContractTest tests MyContract, but may inherit from forge-std's Test, as well as e.g. your own TestUtilities helper contract.
Integration tests should live in the same test directory, with a clear naming convention. These may be in dedicated files, or they may live next to related unit tests in existing test files.
Be consistent with test naming, as it's helpful for filtering tests (e.g. for gas reports you might want to filter out revert tests). When combining naming conventions, keep them alphabetical. Below is a sample of valid names. A comprehensive list of valid and invalid examples can be found here.
- test_Description for standard tests.
- testFuzz_Description for fuzz tests.
- test_Revert[If|When]_Condition for tests expecting a revert.
- testFork_Description for tests that fork from a network.
- testForkFuzz_Revert[If|When]_Condition for a fuzz test that forks and expects a revert.
Name your constants and immutables using ALL_CAPS_WITH_UNDERSCORES, to make it easier to distinguish them from variables and functions.
When using assertions like assertEq, consider leveraging the last string param to make it easier to identify failures. These can be kept brief, or even just be numbers—they basically serve as a replacement for showing line numbers of the revert, e.g. assertEq(x, y, "1") or assertEq(x, y, "sum1"). (Note: foundry-rs/foundry#2328 tracks integrating this natively).
When testing events, prefer setting all expectEmit arguments to true, i.e. vm.expectEmit(true, true, true, true) or vm.expectEmit(). Benefits:
- This ensures you test everything in your event.
- If you add a topic (i.e. a new indexed parameter), it's now tested by default.
- Even if you only have 1 topic, the extra true arguments don't hurt.
Remember to write invariant tests! For the assertion string, use a verbose english description of the invariant: assertEq(x + y, z, "Invariant violated: the sum of x and y must always equal z"). For more info on this, check out the Invariant Testing tutorial.

Fork Tests

Don't feel like you need to give forks tests special treatment, and use them liberally:
- Mocks are required in closed-source web2 development—you have to mock API responses because the code for that API isn't open source so you cannot just run it locally. But for blockchains that's not true: any code you're interacting with that's already deployed can be locally executed and even modified for free. So why introduce the risk of a wrong mock if you don't need to?
- A common reason to avoid fork tests and prefer mocks is that fork tests are slow. But this is not always true. By pinning to a block number, forge caches RPC responses so only the first run is slower, and subsequent runs are significantly faster. See this benchmark, where it took forge 7 minutes for the first run with a remote RPC, but only half a second once data was cached. Alchemy and Infura both offer free archive data, so pinning to a block shouldn't be problematic.
- Note that the foundry-toolchain GitHub Action will cache RPC responses in CI by default, and it will also update the cache when you update your fork tests..
Be careful with fuzz tests on a fork to avoid burning through RPC requests with non-deterministic fuzzing. If the input to your fork fuzz test is some parameter which is used in an RPC call to fetch data (e.g. querying the token balance of an address), each run of a fuzz test uses at least 1 RPC request, so you'll quickly hit rate limits or usage limits. Solutions to consider:
- Replace multiple RPC calls with a single multicall.
- Specify a fuzz/invariant seed: this makes sure each forge test invocation uses the same fuzz inputs. RPC results are cached locally, so you'll only query the node the first time.
- Structure your tests so the data you are fuzzing over is computed locally by your contract, and not data that is used in an RPC call (may or may not be feasible based on what you're doing).
- Lastly, you can of course always run a local node or bump your RPC plan.
When writing fork tests, do not use the --fork-url flag. Instead, prefer the following approach for its improved flexibility:
- Define [rpc_endpoints] in the foundry.toml config file and use the forking cheatcodes.
- Access the RPC URL endpoint in your test with forge-std's stdChains.ChainName.rpcUrl. See the list of supported chains and expected config file aliases here.
- Always pin to a block so tests are deterministic and RPC responses are cached.
- More info on this fork test approach can be found here (this predates StdChains so that aspect is a bit out of date).

Test Harnesses

Internal Functions

To test internal functions, write a harness contract that inherits from the contract under test (CuT). Harness contracts that inherit from the CuT expose the internal functions as external ones.

Each internal function that is tested should be exposed via an external one with a name that follows the pattern exposed_<function_name>. For example:

// file: src/MyContract.sol
contract MyContract {
  function myInternalMethod() internal returns (uint) {
    return 42;
  }
}

// file: test/MyContract.t.sol
import {MyContract} from "src/MyContract.sol";

contract MyContractHarness is MyContract {
  // Deploy this contract then call this method to test `myInternalMethod`.
  function exposed_myInternalMethod() external returns (uint) {
    return myInternalMethod();
  }
}

Private Functions

Unfortunately there is currently no good way to unit test private methods since they cannot be accessed by any other contracts. Options include:

Converting private functions to internal.
Copy/pasting the logic into your test contract and writing a script that runs in CI check to ensure both functions are identical.

Workaround Functions

Harnesses can also be used to expose functionality or information otherwise unavailable in the original smart contract. The most straightforward example is when we want to test the length of a public array. The functions should follow the pattern: workaround_<function_name>, such as workaround_queueLength().

Another use case for this is tracking data that you would not track in production to help test invariants. For example, you might store a list of all token holders to simplify validation of the invariant "sum of all balances must equal total supply". These are often known as "ghost variables". You can learn more about this in Rikard Hjort's Formal Methods for the Working DeFi Dev talk.

Best practices

Thanks to @samsczun's How Do You Even Write Secure Code Anyways talk for the tips in this section and the following section.

Don't optimize for coverage, optimize for well thought-out tests.
Write positive and negative unit tests.
- Write positive unit tests for things that the code should handle. Validate all state that changes from these tests.
- Write negative unit tests for things that the code should not handle. It's helpful to follow up (as an adjacent test) with the positive test and make the change that it needs to pass.
- Each code path should have its own unit test.
Write integration tests to test entire features.
Write fork tests to verify the correct behavior with existing deployed contract.

Taint Analysis

When testing, you should prioritize functions that an attacker can affect, that means functions that accept some kind of user input. These are called sources.

Consider that input data as tainted until it has been checked by the code, at which point it's considered clean.

A sink is a part of the code where some important operation is happening. For example, in MakerDAO that would be vat.sol.

You should ensure that no tainted data ever reaches a sink. That means that all data that find themselves in the sink, should, at some point, have been checked by you. So, you need to define what the data should be and then make sure your checks ensure that the data will be how you expect it to be.

Scripts

Stick with run as the default function name for clarity.
Any methods that are not intended to be called directly in the script should be internal or private. Generally the only public method should be run, as it's easier to read/understand when each script file just does one thing.
Consider prefixing scripts with a number based on the order they're intended to be run over the protocol's lifecycle. For example, 01_Deploy.s.sol, 02_TransferOwnership.s.sol. This makes things more self-documenting. This may not always apply depending on your project.
Test your scripts.
- Unit test them like you would test normal contracts, by writing tests that assert on the state changes made from running the script.
- Write your deploy script and scaffold tests by running that script. Then, run all tests against the state resulting from your production deployment script. This is a great way to gain confidence in a deploy script.
- Within your script itself, use require statements (or the if (condition) revert() pattern if you prefer) to stop execution of your script if something is wrong. For example, require(computedAddress == deployedAddress, "address mismatch"). Using the assertEq helpers instead will not stop execution.
Carefully audit which transactions are broadcast. Transactions not broadcast are still executed in the context of a test, so missing broadcasts or extra broadcasts are easy sources of error in the previous step.
Watch out for frontrunning. Forge simulates your script, generates transaction data from the simulation results, then broadcasts the transactions. Make sure your script is robust against chain-state changing between the simulation and broadcast. A sample script vulnerable to this is below:

// Pseudo-code, may not compile.
contract VulnerableScript is Script {
   function run() public {
      vm.startBroadcast();

      // Transaction 1: Deploy a new Gnosis Safe with CREATE.
      // Because we're using CREATE instead of CREATE2, the address of the new
      // Safe is a function of the nonce of the gnosisSafeProxyFactory.
      address mySafe = gnosisSafeProxyFactory.createProxy(singleton, data);

      // Transaction 2: Send tokens to the new Safe.
      // We know the address of mySafe is a function of the nonce of the
      // gnosisSafeProxyFactory. If someone else deploys a Gnosis Safe between
      // the simulation and broadcast, the address of mySafe will be different,
      // and this script will send 1000 DAI to the other person's Safe. In this
      // case, we can protect ourselves from this by using CREATE2 instead of
      // CREATE, but every situation may have different solutions.
      dai.transfer(mySafe, 1000e18);

      vm.stopBroadcast();
   }
}

For scripts that read from JSON input files, put the input files in script/input/<chainID>/<description>.json. Then have run(string memory input) (or take multiple string inputs if you need to read from multiple files) as the script's signature, and use the below method to read the JSON file.

function readInput(string memory input) internal returns (string memory) {
  string memory inputDir = string.concat(vm.projectRoot(), "/script/input/");
  string memory chainDir = string.concat(vm.toString(block.chainid), "/");
  string memory file = string.concat(input, ".json");
  return vm.readFile(string.concat(inputDir, chainDir, file));
}

Comments

For public or external methods and variables, use NatSpec comments.
- forge doc will parse these to autogenerate documentation.
- Etherscan will display them in the contract UI.
For simple NatSpec comments, consider just documenting params in the docstring, such as /// @notice Returns the sum of `x` and `y`., instead of using @param tags.
For complex NatSpec comments, consider using a tool like PlantUML to generate ASCII art diagrams to help explain complex aspects of the codebase.
Any markdown in your comments will carry over properly when generating docs with forge doc, so structure comments with markdown when useful.
- Good: /// @notice Returns the sum of `x` and `y`.
- Bad: /// @notice Returns the sum of x and y.

Resources

Write more secure code and better tests:

Foundry in Action:

Nomad Monorepo: All the contracts-* packages. Good example of using many Foundry features including fuzzing, ffi and various cheatcodes.
Uniswap Periphery: Good example of using inheritance to isolate test fixtures.
awesome-foundry: A curated list of awesome of the Foundry development framework.
PRBMath: A library for fixed-point arithmetic in Solidity, with many parameterized tests that harness Foundry.

Creating an NFT with Solmate

This tutorial will walk you through creating an OpenSea compatible NFT with Foundry and Solmate. A full implementation of this tutorial can be found here.

This tutorial is for illustrative purposes only and provided on an as-is basis. The tutorial is not audited nor fully tested. No code in this tutorial should be used in a production environment.

Create project and install dependencies

Start by setting up a Foundry project following the steps outlined in the Getting started section. We will also install Solmate for their ERC721 implementation, as well as some OpenZeppelin utility libraries. Install the dependencies by running the following commands from the root of your project:

forge install transmissions11/solmate Openzeppelin/openzeppelin-contracts

These dependencies will be added as git submodules to your project.

If you have followed the instructions correctly your project should be structured like this:

Project structure

Implement a basic NFT

We are then going to rename the boilerplate contract in src/Contract.sol to src/NFT.sol and replace the code:

// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.8.10;

import "solmate/tokens/ERC721.sol";
import "openzeppelin-contracts/contracts/utils/Strings.sol";

contract NFT is ERC721 {
    uint256 public currentTokenId;

    constructor(
        string memory _name,
        string memory _symbol
    ) ERC721(_name, _symbol) {}

    function mintTo(address recipient) public payable returns (uint256) {
        uint256 newItemId = ++currentTokenId;
        _safeMint(recipient, newItemId);
        return newItemId;
    }

    function tokenURI(uint256 id) public view virtual override returns (string memory) {
        return Strings.toString(id);
    }
}

Let's take a look at this very basic implementation of an NFT. We start by importing two contracts from our git submodules. We import solmate's gas optimized implementation of the ERC721 standard which our NFT contract will inherit from. Our constructor takes the _name and _symbol arguments for our NFT and passes them on to the constructor of the parent ERC721 implementation. Lastly we implement the mintTo function which allows anyone to mint an NFT. This function increments the currentTokenId and makes use of the _safeMint function of our parent contract.

Compile & deploy with forge

To compile the NFT contract run forge build. You might experience a build failure due to wrong mapping:

Error:
Compiler run failed
error[6275]: ParserError: Source "lib/openzeppelin-contracts/contracts/contracts/utils/Strings.sol" not found: File not found. Searched the following locations: "/PATH/TO/REPO".
 --> src/NFT.sol:5:1:
  |
5 | import "openzeppelin-contracts/contracts/utils/Strings.sol";
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

this can be fixed by setting up the correct remapping. Create a file remappings.txt in your project and add the line

openzeppelin-contracts/=lib/openzeppelin-contracts/

(You can find out more on remappings in the dependencies documentation.

By default the compiler output will be in the out directory. To deploy our compiled contract with Forge we have to set environment variables for the RPC endpoint and the private key we want to use to deploy.

Set your environment variables by running:

export RPC_URL=<Your RPC endpoint>
export PRIVATE_KEY=<Your wallets private key>

Once set, you can deploy your NFT with Forge by running the below command while adding the relevant constructor arguments to the NFT contract:

forge create NFT --rpc-url=$RPC_URL --private-key=$PRIVATE_KEY --constructor-args <name> <symbol>

If successfully deployed, you will see the deploying wallet's address, the contract's address as well as the transaction hash printed to your terminal.

Minting NFTs from your contract

Calling functions on your NFT contract is made simple with Cast, Foundry's command-line tool for interacting with smart contracts, sending transactions, and getting chain data. Let's have a look at how we can use it to mint NFTs from our NFT contract.

Given that you already set your RPC and private key env variables during deployment, mint an NFT from your contract by running:

cast send --rpc-url=$RPC_URL <contractAddress>  "mintTo(address)" <arg> --private-key=$PRIVATE_KEY

Well done! You just minted your first NFT from your contract. You can sanity check the owner of the NFT with currentTokenId equal to 1 by running the below cast call command. The address you provided above should be returned as the owner.

cast call --rpc-url=$RPC_URL --private-key=$PRIVATE_KEY <contractAddress> "ownerOf(uint256)" 1

Extending our NFT contract functionality and testing

Let's extend our NFT by adding metadata to represent the content of our NFTs, as well as set a minting price, a maximum supply and the possibility to withdraw the collected proceeds from minting. To follow along you can replace your current NFT contract with the code snippet below:

// SPDX-License-Identifier: UNLICENSED
pragma solidity >=0.8.10;

import "solmate/tokens/ERC721.sol";
import "openzeppelin-contracts/contracts/utils/Strings.sol";
import "openzeppelin-contracts/contracts/access/Ownable.sol";

error MintPriceNotPaid();
error MaxSupply();
error NonExistentTokenURI();
error WithdrawTransfer();

contract NFT is ERC721, Ownable {

    using Strings for uint256;
    string public baseURI;
    uint256 public currentTokenId;
    uint256 public constant TOTAL_SUPPLY = 10_000;
    uint256 public constant MINT_PRICE = 0.08 ether;

    constructor(
        string memory _name,
        string memory _symbol,
        string memory _baseURI
    ) ERC721(_name, _symbol) {
        baseURI = _baseURI;
    }

    function mintTo(address recipient) public payable returns (uint256) {
        if (msg.value != MINT_PRICE) {
            revert MintPriceNotPaid();
        }
        uint256 newTokenId = ++currentTokenId;
        if (newTokenId > TOTAL_SUPPLY) {
            revert MaxSupply();
        }
        _safeMint(recipient, newTokenId);
        return newTokenId;
    }

    function tokenURI(uint256 tokenId)
        public
        view
        virtual
        override
        returns (string memory)
    {
        if (ownerOf(tokenId) == address(0)) {
            revert NonExistentTokenURI();
        }
        return
            bytes(baseURI).length > 0
                ? string(abi.encodePacked(baseURI, tokenId.toString()))
                : "";
    }

    function withdrawPayments(address payable payee) external onlyOwner {
        uint256 balance = address(this).balance;
        (bool transferTx, ) = payee.call{value: balance}("");
        if (!transferTx) {
            revert WithdrawTransfer();
        }
    }
}

Among other things, we have added metadata that can be queried from any front-end application like OpenSea, by calling the tokenURI method on our NFT contract.

Note: If you want to provide a real URL to the constructor at deployment, and host the metadata of this NFT contract please follow the steps outlined here.

Let's test some of this added functionality to make sure it works as intended. Foundry offers an extremely fast EVM native testing framework through Forge.

Within your test folder rename the current Contract.t.sol test file to NFT.t.sol. This file will contain all tests regarding the NFT's mintTo method. Next, replace the existing boilerplate code with the below:

// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.8.10;

import "forge-std/Test.sol";
import "../src/NFT.sol";

contract NFTTest is Test {
    using stdStorage for StdStorage;

    NFT private nft;

    function setUp() public {
        // Deploy NFT contract
        nft = new NFT("NFT_tutorial", "TUT", "baseUri");
    }

    function test_RevertMintWithoutValue() public {
        vm.expectRevert(MintPriceNotPaid.selector);
        nft.mintTo(address(1));
    }

    function test_MintPricePaid() public {
        nft.mintTo{value: 0.08 ether}(address(1));
    }

    function test_RevertMintMaxSupplyReached() public {
        uint256 slot = stdstore
            .target(address(nft))
            .sig("currentTokenId()")
            .find();
        bytes32 loc = bytes32(slot);
        bytes32 mockedCurrentTokenId = bytes32(abi.encode(10000));
        vm.store(address(nft), loc, mockedCurrentTokenId);
        vm.expectRevert(MaxSupply.selector);
        nft.mintTo{value: 0.08 ether}(address(1));
    }

    function test_RevertMintToZeroAddress() public {
        vm.expectRevert("INVALID_RECIPIENT");
        nft.mintTo{value: 0.08 ether}(address(0));
    }

    function test_NewMintOwnerRegistered() public {
        nft.mintTo{value: 0.08 ether}(address(1));
        uint256 slotOfNewOwner = stdstore
            .target(address(nft))
            .sig(nft.ownerOf.selector)
            .with_key(1)
            .find();

        uint160 ownerOfTokenIdOne = uint160(
            uint256(
                (vm.load(address(nft), bytes32(abi.encode(slotOfNewOwner))))
            )
        );
        assertEq(address(ownerOfTokenIdOne), address(1));
    }

    function test_BalanceIncremented() public {
        nft.mintTo{value: 0.08 ether}(address(1));
        uint256 slotBalance = stdstore
            .target(address(nft))
            .sig(nft.balanceOf.selector)
            .with_key(address(1))
            .find();

        uint256 balanceFirstMint = uint256(
            vm.load(address(nft), bytes32(slotBalance))
        );
        assertEq(balanceFirstMint, 1);

        nft.mintTo{value: 0.08 ether}(address(1));
        uint256 balanceSecondMint = uint256(
            vm.load(address(nft), bytes32(slotBalance))
        );
        assertEq(balanceSecondMint, 2);
    }

    function test_SafeContractReceiver() public {
        Receiver receiver = new Receiver();
        nft.mintTo{value: 0.08 ether}(address(receiver));
        uint256 slotBalance = stdstore
            .target(address(nft))
            .sig(nft.balanceOf.selector)
            .with_key(address(receiver))
            .find();

        uint256 balance = uint256(vm.load(address(nft), bytes32(slotBalance)));
        assertEq(balance, 1);
    }

    function test_RevertUnSafeContractReceiver() public {
        vm.etch(address(1), bytes("mock code"));
        vm.expectRevert(bytes(""));
        nft.mintTo{value: 0.08 ether}(address(1));
    }

    function test_WithdrawalWorksAsOwner() public {
        // Mint an NFT, sending eth to the contract
        Receiver receiver = new Receiver();
        address payable payee = payable(address(0x1337));
        uint256 priorPayeeBalance = payee.balance;
        nft.mintTo{value: nft.MINT_PRICE()}(address(receiver));
        // Check that the balance of the contract is correct
        assertEq(address(nft).balance, nft.MINT_PRICE());
        uint256 nftBalance = address(nft).balance;
        // Withdraw the balance and assert it was transferred
        nft.withdrawPayments(payee);
        assertEq(payee.balance, priorPayeeBalance + nftBalance);
    }

    function test_WithdrawalFailsAsNotOwner() public {
        // Mint an NFT, sending eth to the contract
        Receiver receiver = new Receiver();
        nft.mintTo{value: nft.MINT_PRICE()}(address(receiver));
        // Check that the balance of the contract is correct
        assertEq(address(nft).balance, nft.MINT_PRICE());
        // Confirm that a non-owner cannot withdraw
        vm.expectRevert("Ownable: caller is not the owner");
        vm.startPrank(address(0xd3ad));
        nft.withdrawPayments(payable(address(0xd3ad)));
        vm.stopPrank();
    }
}

contract Receiver is ERC721TokenReceiver {
    function onERC721Received(
        address operator,
        address from,
        uint256 id,
        bytes calldata data
    ) external override returns (bytes4) {
        return this.onERC721Received.selector;
    }
}

The test suite is set up as a contract with a setUp method which runs before every individual test.

As you can see, Forge offers a number of cheatcodes to manipulate state to accommodate your testing scenario.

For example, our testFailMaxSupplyReached test checks that an attempt to mint fails when the max supply of NFT is reached. Thus, the currentTokenId of the NFT contract needs to be set to the max supply by using the store cheatcode which allows you to write data to your contracts storage slots. The storage slots you wish to write to can easily be found using the forge-std helper library. You can run the test with the following command:

forge test

If you want to put your Forge skills to practice, write tests for the remaining methods of our NFT contract. Feel free to PR them to nft-tutorial, where you will find the full implementation of this tutorial.

Gas reports for your function calls

Foundry provides comprehensive gas reports about your contracts. For every function called within your tests, it returns the minimum, average, median and max gas cost. To print the gas report simply run:

forge test --gas-report

This comes in handy when looking at various gas optimizations within your contracts.

Let's have a look at the gas savings we made by substituting OpenZeppelin with Solmate for our ERC721 implementation. You can find the NFT implementation using both libraries here. Below are the resulting gas reports when running forge test --gas-report on that repository.

As you can see, our implementation using Solmate saves around 500 gas on a successful mint (the max gas cost of the mintTo function calls).

Gas report solmate NFT

Gas report OZ NFT

That's it, I hope this will give you a good practical basis of how to get started with foundry. We think there is no better way to deeply understand solidity than writing your tests in solidity. You will also experience less context switching between javascript and solidity. Happy coding!

Note: Follow this tutorial to learn how to deploy the NFT contract used here with solidity scripting.

Dockerizing a Foundry project

This tutorial shows you how to build, test, and deploy a smart contract using Foundry's Docker image. It adapts code from the solmate nft tutorial. If you haven't completed that tutorial yet, and are new to solidity, you may want to start with it first. Alternatively, if you have some familiarity with Docker and Solidity, you can use your own existing project and adjust accordingly. The full source code for both the NFT and the Docker stuff is available here.

This tutorial is for illustrative purposes only and provided on an as-is basis. The tutorial is not audited nor fully tested. No code in this tutorial should be used in a production environment.

Installation and Setup

The only installation required to run this tutorial is Docker, and optionally, an IDE of your choice. Follow the Docker installation instructions.

To keep future commands succinct, let's re-tag the image:
docker tag ghcr.io/foundry-rs/foundry:latest foundry:latest

Having Foundry installed locally is not strictly required, but it may be helpful for debugging. You can install it using foundryup.

Finally, to use any of the cast or forge create portions of this tutorial, you will need access to an Ethereum node. If you don't have your own node running (likely), you can use a 3rd party node service. We won't recommend a specific provider in this tutorial. A good place to start learning about Nodes-as-a-Service is Ethereum's article on the subject.

For the rest of this tutorial, it is assumed that the RPC endpoint of your ethereum node is set like this: export RPC_URL=<YOUR_RPC_URL>

A tour around the Foundry docker image

The docker image can be used in two primary ways:

As an interface directly to forge and cast
As a base image for building your own containerized test, build, and deployment tooling

We will cover both, but let's start by taking a look at interfacing with foundry using docker. This is also a good test that your local installation worked!

We can run any of the cast commands against our docker image. Let's fetch the latest block information:

$ docker run foundry "cast block --rpc-url $RPC_URL latest"
baseFeePerGas        "0xb634241e3"
difficulty           "0x2e482bdf51572b"
extraData            "0x486976656f6e20686b"
gasLimit             "0x1c9c380"
gasUsed              "0x652993"
hash                 "0x181748772da2f968bcc91940c8523bb6218a7d57669ded06648c9a9fb6839db5"
logsBloom            "0x406010046100001198c220108002b606400029444814008210820c04012804131847150080312500300051044208430002008029880029011520380060262400001c538d00440a885a02219d49624aa110000003094500022c003600a00258009610c410323580032000849a0408a81a0a060100022505202280c61880c80020e080244400440404520d210429a0000400010089410c8408162903609c920014028a94019088681018c909980701019201808040004100000080540610a9144d050020220c10a24c01c000002005400400022420140e18100400e10254926144c43a200cc008142080854088100128844003010020c344402386a8c011819408"
miner                "0x1ad91ee08f21be3de0ba2ba6918e714da6b45836"
mixHash              "0xb920857687476c1bcb21557c5f6196762a46038924c5f82dc66300347a1cfc01"
nonce                "0x1ce6929033fbba90"
number               "0xdd3309"
parentHash           "0x39c6e1aa997d18a655c6317131589fd327ae814ef84e784f5eb1ab54b9941212"
receiptsRoot         "0x4724f3b270dcc970f141e493d8dc46aeba6fffe57688210051580ac960fe0037"
sealFields           []
sha3Uncles           "0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347"
size                 "0x1d6bb"
stateRoot            "0x0d4b714990132cf0f21801e2931b78454b26aad706fc6dc16b64e04f0c14737a"
timestamp            "0x6246259b"
totalDifficulty      "0x9923da68627095fd2e7"
transactions         [...]
uncles               []

If we're in a directory with some Solidity source code, we can mount that directory into docker and use forge however we wish. For example:

$ docker run -v $PWD:/app foundry "forge test --root /app --watch"
No files changed, compilation skipped

Running 8 tests for test/OpenZeppelinNft.t.sol:OpenZeppelinNftTests
[PASS] testBalanceIncremented() (gas: 217829)
[PASS] testFailMaxSupplyReached() (gas: 134524)
[PASS] testFailMintToZeroAddress() (gas: 34577)
[PASS] testFailNoMintPricePaid() (gas: 5568)
[PASS] testFailUnSafeContractReceiver() (gas: 88276)
[PASS] testMintPricePaid() (gas: 81554)
[PASS] testNewMintOwnerRegistered() (gas: 190956)
[PASS] testSafeContractReceiver() (gas: 273132)
Test result: ok. 8 passed; 0 failed; finished in 2.68ms

Running 8 tests for test/SolmateNft.sol:SolmateNftTests
[PASS] testBalanceIncremented() (gas: 217400)
[PASS] testFailMaxSupplyReached() (gas: 134524)
[PASS] testFailMintToZeroAddress() (gas: 34521)
[PASS] testFailNoMintPricePaid() (gas: 5568)
[PASS] testFailUnSafeContractReceiver() (gas: 87807)
[PASS] testMintPricePaid() (gas: 81321)
[PASS] testNewMintOwnerRegistered() (gas: 190741)
[PASS] testSafeContractReceiver() (gas: 272636)
Test result: ok. 8 passed; 0 failed; finished in 2.79ms

You can see our code was compiled and tested entirely within the container. Also, since we passed the --watch option, the container will recompile the code whenever a change is detected.

Note: The Foundry docker image is built on alpine and designed to be as slim as possible. For this reason, it does not currently include development resources like git. If you are planning to manage your entire development lifecycle within the container, you should build a custom development image on top of Foundry's image.

Creating a "build and test" image

Let's use the Foundry docker image as a base for using our own Docker image. We'll use the image to:

Build our solidity code
Run our solidity tests

A simple Dockerfile can accomplish these two goals:

# Use the latest foundry image
FROM ghcr.io/foundry-rs/foundry

# Copy our source code into the container
WORKDIR /app

# Build and test the source code
COPY . .
RUN forge build
RUN forge test

You can build this docker image and watch forge build/run the tests within the container:

$ docker build --no-cache --progress=plain .

Now, what happens if one of our tests fails? Modify src/test/NFT.t.sol as you please to make one of the tests fails. Try to build image again.

$ docker build --no-cache --progress=plain .
<...>
#9 0.522 Failed tests:
#9 0.522 [FAIL. Reason: Ownable: caller is not the owner] testWithdrawalFailsAsNotOwner() (gas: 193917)
#9 0.522
#9 0.522 Encountered a total of 1 failing tests, 9 tests succeeded
------
error: failed to solve: executor failed running [/bin/sh -c forge test]: exit code: 1

Our image failed to build because our tests failed! This is actually a nice property, because it means if we have a Docker image that successfully built (and therefore is available for use), we know the code inside the image passed the tests.*

*Of course, chain of custody of your docker images is very important. Docker layer hashes can be very useful for verification. In a production environment, consider signing your docker images.

Creating a deployer image

Now, we'll move on to a bit more of an advanced Dockerfile. Let's add an entrypoint that allows us to deploy our code by using the built (and tested!) image. We can target the Rinkeby testnet first.

# Use the latest foundry image
FROM ghcr.io/foundry-rs/foundry

# Copy our source code into the container
WORKDIR /app

# Build and test the source code
COPY . .
RUN forge build
RUN forge test

# Set the entrypoint to the forge deployment command
ENTRYPOINT ["forge", "create"]

Let's build the image, this time giving it a name:

$ docker build --no-cache --progress=plain -t nft-deployer .

Here's how we can use our docker image to deploy:

$ docker run nft-deployer --rpc-url $RPC_URL --constructor-args "ForgeNFT" "FNFT" "https://ethereum.org" --private-key $PRIVATE_KEY ./src/NFT.sol:NFT
No files changed, compilation skipped
Deployer: 0x496e09fcb240c33b8fda3b4b74d81697c03b6b3d
Deployed to: 0x23d465eaa80ad2e5cdb1a2345e4b54edd12560d3
Transaction hash: 0xf88c68c4a03a86b0e7ecb05cae8dea36f2896cd342a6af978cab11101c6224a9

We've just built, tested, and deployed our contract entirely within a docker container! This tutorial was intended for testnet, but you can run the exact same Docker image targeting mainnet and be confident that the same code is being deployed by the same tooling.

Why is this useful?

Docker is about portability, reproducibility, and environment invariance. This means you can be less concerned about unexpected changes when you switch between environments, networks, developers, etc. Here are a few basic examples of why I like to use Docker images for smart contract deployment:

Reduces overhead of ensuring system level dependencies match between deployment environments (e.g. does your production runner always have the same version of forge as your dev runner?)
Increases confidence that code has been tested prior to deployment and has not been altered (e.g. if, in the above image, your code re-compiles on deployment, that's a major red flag).
Eases pain points around segregation of duties: people with your mainnet credentials do not need to ensure they have the latest compiler, codebase, etc. It's easy to ensure that the docker deploy image someone ran in testnet is identical to the one targeting mainnet.
At the risk of sounding web2, Docker is an accepted standard on virtually all public cloud providers. It makes it easy to schedule jobs, tasks, etc that need to interact with the blockchain.

Troubleshooting

As noted above, the Foundry image does not include git by default. This can cause certain commands to fail without a clear cause. For example:

$ docker run foundry "forge init --no-git /test"
Initializing /test...
Installing ds-test in "/test/lib/ds-test", (url: https://github.com/dapphub/ds-test, tag: None)
Error:
   0: No such file or directory (os error 2)

Location:
   cli/src/cmd/forge/install.rs:107

In this case, the failure is still caused by a missing git installation. The recommended fix is to build off the existing Foundry image and install any additional development dependencies you need.

Testing EIP-712 Signatures

Intro

EIP-712 introduced the ability to sign transactions off-chain which other users can later execute on-chain. A common example is EIP-2612 gasless token approvals.

Traditionally, setting a user or contract allowance to transfer ERC-20 tokens from an owner's balance required the owner to submit an approval on-chain. As this proved to be poor UX, DAI introduced ERC-20 permit (later standardized as EIP-2612) allowing the owner to sign the approval off-chain which the spender (or anyone else!) can submit on-chain prior to the transferFrom.

This guide will cover testing this pattern in Solidity using Foundry.

Diving In

First we'll cover a basic token transfer:

Owner signs approval off-chain
Spender calls permit and transferFrom on-chain

We'll use Solmate's ERC-20, as EIP-712 and EIP-2612 batteries come included. Take a glance over the full contract if you haven't already - here is permit implemented:

    /*//////////////////////////////////////////////////////////////
                             EIP-2612 LOGIC
    //////////////////////////////////////////////////////////////*/

    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) public virtual {
        require(deadline >= block.timestamp, "PERMIT_DEADLINE_EXPIRED");

        // Unchecked because the only math done is incrementing
        // the owner's nonce which cannot realistically overflow.
        unchecked {
            address recoveredAddress = ecrecover(
                keccak256(
                    abi.encodePacked(
                        "\x19\x01",
                        DOMAIN_SEPARATOR(),
                        keccak256(
                            abi.encode(
                                keccak256(
                                    "Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)"
                                ),
                                owner,
                                spender,
                                value,
                                nonces[owner]++,
                                deadline
                            )
                        )
                    )
                ),
                v,
                r,
                s
            );

            require(recoveredAddress != address(0) && recoveredAddress == owner, "INVALID_SIGNER");

            allowance[recoveredAddress][spender] = value;
        }

        emit Approval(owner, spender, value);
    }

We'll also be using a custom SigUtils contract to help create, hash, and sign the approvals off-chain.

// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.8.13;

contract SigUtils {
    bytes32 internal DOMAIN_SEPARATOR;

    constructor(bytes32 _DOMAIN_SEPARATOR) {
        DOMAIN_SEPARATOR = _DOMAIN_SEPARATOR;
    }

    // keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
    bytes32 public constant PERMIT_TYPEHASH =
        0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;

    struct Permit {
        address owner;
        address spender;
        uint256 value;
        uint256 nonce;
        uint256 deadline;
    }

    // computes the hash of a permit
    function getStructHash(Permit memory _permit)
        internal
        pure
        returns (bytes32)
    {
        return
            keccak256(
                abi.encode(
                    PERMIT_TYPEHASH,
                    _permit.owner,
                    _permit.spender,
                    _permit.value,
                    _permit.nonce,
                    _permit.deadline
                )
            );
    }

    // computes the hash of the fully encoded EIP-712 message for the domain, which can be used to recover the signer
    function getTypedDataHash(Permit memory _permit)
        public
        view
        returns (bytes32)
    {
        return
            keccak256(
                abi.encodePacked(
                    "\x19\x01",
                    DOMAIN_SEPARATOR,
                    getStructHash(_permit)
                )
            );
    }
}

Handling Dynamic Values

While the Permit struct passed in the getStructHash() function above doesn't contain any dynamic value types, if you're using them it's important to remember that 'bytes' and 'string' types must be encoded as a 'keccak256' hash of their contents. More on this aspect of the EIP 712 Spec here.

Setup

Deploy a mock ERC-20 token and SigUtils helper with the token's EIP-712 domain separator
Create private keys to mock the owner and spender
Derive their addresses using the vm.addr cheatcode
Mint the owner a test token

contract ERC20Test is Test {
    MockERC20 internal token;
    SigUtils internal sigUtils;

    uint256 internal ownerPrivateKey;
    uint256 internal spenderPrivateKey;

    address internal owner;
    address internal spender;

    function setUp() public {
        token = new MockERC20();
        sigUtils = new SigUtils(token.DOMAIN_SEPARATOR());

        ownerPrivateKey = 0xA11CE;
        spenderPrivateKey = 0xB0B;

        owner = vm.addr(ownerPrivateKey);
        spender = vm.addr(spenderPrivateKey);

        token.mint(owner, 1e18);
    }

Testing: permit

Create an approval for the spender
Compute its digest using sigUtils.getTypedDataHash
Sign the digest using the vm.sign cheatcode with the owner's private key
Store the uint8 v, bytes32 r, bytes32 s of the signature
Call permit with the signed permit and signature to execute the approval on-chain

    function test_Permit() public {
        SigUtils.Permit memory permit = SigUtils.Permit({
            owner: owner,
            spender: spender,
            value: 1e18,
            nonce: 0,
            deadline: 1 days
        });

        bytes32 digest = sigUtils.getTypedDataHash(permit);

        (uint8 v, bytes32 r, bytes32 s) = vm.sign(ownerPrivateKey, digest);

        token.permit(
            permit.owner,
            permit.spender,
            permit.value,
            permit.deadline,
            v,
            r,
            s
        );

        assertEq(token.allowance(owner, spender), 1e18);
        assertEq(token.nonces(owner), 1);
    }

Ensure failure for calls with an expired deadline, invalid signer, invalid nonce, and signature replay

    function testRevert_ExpiredPermit() public {
        SigUtils.Permit memory permit = SigUtils.Permit({
            owner: owner,
            spender: spender,
            value: 1e18,
            nonce: token.nonces(owner),
            deadline: 1 days
        });

        bytes32 digest = sigUtils.getTypedDataHash(permit);

        (uint8 v, bytes32 r, bytes32 s) = vm.sign(ownerPrivateKey, digest);

        vm.warp(1 days + 1 seconds); // fast forward one second past the deadline

        vm.expectRevert("PERMIT_DEADLINE_EXPIRED");
        token.permit(
            permit.owner,
            permit.spender,
            permit.value,
            permit.deadline,
            v,
            r,
            s
        );
    }

    function testRevert_InvalidSigner() public {
        SigUtils.Permit memory permit = SigUtils.Permit({
            owner: owner,
            spender: spender,
            value: 1e18,
            nonce: token.nonces(owner),
            deadline: 1 days
        });

        bytes32 digest = sigUtils.getTypedDataHash(permit);

        (uint8 v, bytes32 r, bytes32 s) = vm.sign(spenderPrivateKey, digest); // spender signs owner's approval

        vm.expectRevert("INVALID_SIGNER");
        token.permit(
            permit.owner,
            permit.spender,
            permit.value,
            permit.deadline,
            v,
            r,
            s
        );
    }

    function testRevert_InvalidNonce() public {
        SigUtils.Permit memory permit = SigUtils.Permit({
            owner: owner,
            spender: spender,
            value: 1e18,
            nonce: 1, // owner nonce stored on-chain is 0
            deadline: 1 days
        });

        bytes32 digest = sigUtils.getTypedDataHash(permit);

        (uint8 v, bytes32 r, bytes32 s) = vm.sign(ownerPrivateKey, digest);

        vm.expectRevert("INVALID_SIGNER");
        token.permit(
            permit.owner,
            permit.spender,
            permit.value,
            permit.deadline,
            v,
            r,
            s
        );
    }

    function testRevert_SignatureReplay() public {
        SigUtils.Permit memory permit = SigUtils.Permit({
            owner: owner,
            spender: spender,
            value: 1e18,
            nonce: 0,
            deadline: 1 days
        });

        bytes32 digest = sigUtils.getTypedDataHash(permit);

        (uint8 v, bytes32 r, bytes32 s) = vm.sign(ownerPrivateKey, digest);

        token.permit(
            permit.owner,
            permit.spender,
            permit.value,
            permit.deadline,
            v,
            r,
            s
        );

        vm.expectRevert("INVALID_SIGNER");
        token.permit(
            permit.owner,
            permit.spender,
            permit.value,
            permit.deadline,
            v,
            r,
            s
        );
    }

Testing: transferFrom

Create, sign, and execute an approval for the spender
Call tokenTransfer as the spender using the vm.prank cheatcode to execute the transfer

    function test_TransferFromLimitedPermit() public {
        SigUtils.Permit memory permit = SigUtils.Permit({
            owner: owner,
            spender: spender,
            value: 1e18,
            nonce: 0,
            deadline: 1 days
        });

        bytes32 digest = sigUtils.getTypedDataHash(permit);

        (uint8 v, bytes32 r, bytes32 s) = vm.sign(ownerPrivateKey, digest);

        token.permit(
            permit.owner,
            permit.spender,
            permit.value,
            permit.deadline,
            v,
            r,
            s
        );

        vm.prank(spender);
        token.transferFrom(owner, spender, 1e18);

        assertEq(token.balanceOf(owner), 0);
        assertEq(token.balanceOf(spender), 1e18);
        assertEq(token.allowance(owner, spender), 0);
    }

    function test_TransferFromMaxPermit() public {
        SigUtils.Permit memory permit = SigUtils.Permit({
            owner: owner,
            spender: spender,
            value: type(uint256).max,
            nonce: 0,
            deadline: 1 days
        });

        bytes32 digest = sigUtils.getTypedDataHash(permit);

        (uint8 v, bytes32 r, bytes32 s) = vm.sign(ownerPrivateKey, digest);

        token.permit(
            permit.owner,
            permit.spender,
            permit.value,
            permit.deadline,
            v,
            r,
            s
        );

        vm.prank(spender);
        token.transferFrom(owner, spender, 1e18);

        assertEq(token.balanceOf(owner), 0);
        assertEq(token.balanceOf(spender), 1e18);
        assertEq(token.allowance(owner, spender), type(uint256).max);
    }

Ensure failure for calls with an invalid allowance and invalid balance

    function testFail_InvalidAllowance() public {
        SigUtils.Permit memory permit = SigUtils.Permit({
            owner: owner,
            spender: spender,
            value: 5e17, // approve only 0.5 tokens
            nonce: 0,
            deadline: 1 days
        });

        bytes32 digest = sigUtils.getTypedDataHash(permit);

        (uint8 v, bytes32 r, bytes32 s) = vm.sign(ownerPrivateKey, digest);

        token.permit(
            permit.owner,
            permit.spender,
            permit.value,
            permit.deadline,
            v,
            r,
            s
        );

        vm.prank(spender);
        token.transferFrom(owner, spender, 1e18); // attempt to transfer 1 token
    }

    function testFail_InvalidBalance() public {
        SigUtils.Permit memory permit = SigUtils.Permit({
            owner: owner,
            spender: spender,
            value: 2e18, // approve 2 tokens
            nonce: 0,
            deadline: 1 days
        });

        bytes32 digest = sigUtils.getTypedDataHash(permit);

        (uint8 v, bytes32 r, bytes32 s) = vm.sign(ownerPrivateKey, digest);

        token.permit(
            permit.owner,
            permit.spender,
            permit.value,
            permit.deadline,
            v,
            r,
            s
        );

        vm.prank(spender);
        token.transferFrom(owner, spender, 2e18); // attempt to transfer 2 tokens (owner only owns 1)
    }

Bundled Example

Here is a section of a mock contract that just deposits ERC-20 tokens. Note how deposit requires a preliminary approve or permit tx in order to transfer tokens, while depositWithPermit sets the allowance and transfers the tokens in a single tx.

    ///                                                          ///
    ///                           DEPOSIT                        ///
    ///                                                          ///

    /// @notice Deposits ERC-20 tokens (requires pre-approval)
    /// @param _tokenContract The ERC-20 token address
    /// @param _amount The number of tokens
    function deposit(address _tokenContract, uint256 _amount) external {
        ERC20(_tokenContract).transferFrom(msg.sender, address(this), _amount);

        userDeposits[msg.sender][_tokenContract] += _amount;

        emit TokenDeposit(msg.sender, _tokenContract, _amount);
    }

    ///                                                          ///
    ///                      DEPOSIT w/ PERMIT                   ///
    ///                                                          ///

    /// @notice Deposits ERC-20 tokens with a signed approval
    /// @param _tokenContract The ERC-20 token address
    /// @param _amount The number of tokens to transfer
    /// @param _owner The user signing the approval
    /// @param _spender The user to transfer the tokens (ie this contract)
    /// @param _value The number of tokens to approve the spender
    /// @param _deadline The timestamp the permit expires
    /// @param _v The 129th byte and chain id of the signature
    /// @param _r The first 64 bytes of the signature
    /// @param _s Bytes 64-128 of the signature
    function depositWithPermit(
        address _tokenContract,
        uint256 _amount,
        address _owner,
        address _spender,
        uint256 _value,
        uint256 _deadline,
        uint8 _v,
        bytes32 _r,
        bytes32 _s
    ) external {
        ERC20(_tokenContract).permit(
            _owner,
            _spender,
            _value,
            _deadline,
            _v,
            _r,
            _s
        );

        ERC20(_tokenContract).transferFrom(_owner, address(this), _amount);

        userDeposits[_owner][_tokenContract] += _amount;

        emit TokenDeposit(_owner, _tokenContract, _amount);
    }

Setup

Deploy the Deposit contract, a mock ERC-20 token, and SigUtils helper with the token's EIP-712 domain separator
Create a private key to mock the owner (the spender is now the Deposit address)
Derive the owner address using the vm.addr cheatcode
Mint the owner a test token

contract DepositTest is Test {
    Deposit internal deposit;
    MockERC20 internal token;
    SigUtils internal sigUtils;

    uint256 internal ownerPrivateKey;
    address internal owner;

    function setUp() public {
        deposit = new Deposit();
        token = new MockERC20();
        sigUtils = new SigUtils(token.DOMAIN_SEPARATOR());

        ownerPrivateKey = 0xA11CE;
        owner = vm.addr(ownerPrivateKey);

        token.mint(owner, 1e18);
    }

Testing: depositWithPermit

Create an approval for the Deposit contract
Compute its digest using sigUtils.getTypedDataHash
Sign the digest using the vm.sign cheatcode with the owner's private key
Store the uint8 v, bytes32 r, bytes32 s of the signature
- Note: can convert to bytes via bytes signature = abi.encodePacked(r, s, v)
Call depositWithPermit with the signed approval and signature to transfer the tokens into the contract

    function test_DepositWithLimitedPermit() public {
        SigUtils.Permit memory permit = SigUtils.Permit({
            owner: owner,
            spender: address(deposit),
            value: 1e18,
            nonce: token.nonces(owner),
            deadline: 1 days
        });

        bytes32 digest = sigUtils.getTypedDataHash(permit);

        (uint8 v, bytes32 r, bytes32 s) = vm.sign(ownerPrivateKey, digest);

        deposit.depositWithPermit(
            address(token),
            1e18,
            permit.owner,
            permit.spender,
            permit.value,
            permit.deadline,
            v,
            r,
            s
        );

        assertEq(token.balanceOf(owner), 0);
        assertEq(token.balanceOf(address(deposit)), 1e18);

        assertEq(token.allowance(owner, address(deposit)), 0);
        assertEq(token.nonces(owner), 1);

        assertEq(deposit.userDeposits(owner, address(token)), 1e18);
    }

    function test_DepositWithMaxPermit() public {
        SigUtils.Permit memory permit = SigUtils.Permit({
            owner: owner,
            spender: address(deposit),
            value: type(uint256).max,
            nonce: token.nonces(owner),
            deadline: 1 days
        });

        bytes32 digest = sigUtils.getTypedDataHash(permit);

        (uint8 v, bytes32 r, bytes32 s) = vm.sign(ownerPrivateKey, digest);

        deposit.depositWithPermit(
            address(token),
            1e18,
            permit.owner,
            permit.spender,
            permit.value,
            permit.deadline,
            v,
            r,
            s
        );

        assertEq(token.balanceOf(owner), 0);
        assertEq(token.balanceOf(address(deposit)), 1e18);

        assertEq(token.allowance(owner, address(deposit)), type(uint256).max);
        assertEq(token.nonces(owner), 1);

        assertEq(deposit.userDeposits(owner, address(token)), 1e18);
    }

Ensure failure for invalid permit and transferFrom calls as previously shown

TLDR

Use Foundry cheatcodes addr, sign, and prank to test EIP-712 signatures in Foundry.

All source code can be found here.

Solidity Scripting

Introduction

Solidity scripting is a way to declaratively deploy contracts using Solidity, instead of using the more limiting and less user friendly forge create.

Solidity scripts are like the scripts you write when working with tools like Hardhat; what makes Solidity scripting different is that they are written in Solidity instead of JavaScript, and they are run on the fast Foundry EVM backend, which provides dry-run capabilities.

High Level Overview

forge script does not work in a sync manner. First, it collects all transactions from the script, and only then does it broadcast them all. It can essentially be split into 4 phases:

Local Simulation - The contract script is run in a local evm. If a rpc/fork url has been provided, it will execute the script in that context. Any external call (not static, not internal) from a vm.broadcast and/or vm.startBroadcast will be appended to a list.
Onchain Simulation - Optional. If a rpc/fork url has been provided, then it will sequentially execute all the collected transactions from the previous phase here.
Broadcasting - Optional. If the --broadcast flag is provided and the previous phases have succeeded, it will broadcast the transactions collected at step 1. and simulated at step 2.
Verification - Optional. If the --verify flag is provided, there's an API key, and the previous phases have succeeded it will attempt to verify the contract. (eg. etherscan).

Given this flow, it's important to be aware that transactions whose behaviour can be influenced by external state/actors might have a different result than what was simulated on step 2. Eg. frontrunning.

Set Up

Let’s try to deploy the NFT contract made in the solmate tutorial with solidity scripting. First of all, we would need to create a new Foundry project via:

forge init solidity-scripting

Since the NFT contract from the solmate tutorial inherits both solmate and OpenZeppelin contracts, we’ll have to install them as dependencies by running:

# Enter the project
cd solidity-scripting

# Install Solmate and OpenZeppelin contracts as dependencies
forge install transmissions11/solmate Openzeppelin/openzeppelin-contracts

Next, we have to delete the Counter.sol file in the src folder and create another file called NFT.sol. You can do this by running:

rm src/Counter.sol test/Counter.t.sol && touch src/NFT.sol && ls src

set up commands

Once that’s done, you should open up your preferred code editor and copy the code below into the NFT.sol file.

// SPDX-License-Identifier: UNLICENSED
pragma solidity >=0.8.10;

import "solmate/tokens/ERC721.sol";
import "openzeppelin-contracts/contracts/utils/Strings.sol";
import "openzeppelin-contracts/contracts/access/Ownable.sol";

error MintPriceNotPaid();
error MaxSupply();
error NonExistentTokenURI();
error WithdrawTransfer();

contract NFT is ERC721, Ownable {

    using Strings for uint256;
    string public baseURI;
    uint256 public currentTokenId;
    uint256 public constant TOTAL_SUPPLY = 10_000;
    uint256 public constant MINT_PRICE = 0.08 ether;

    constructor(
        string memory _name,
        string memory _symbol,
        string memory _baseURI
    ) ERC721(_name, _symbol) {
        baseURI = _baseURI;
    }

    function mintTo(address recipient) public payable returns (uint256) {
        if (msg.value != MINT_PRICE) {
            revert MintPriceNotPaid();
        }
        uint256 newTokenId = ++currentTokenId;
        if (newTokenId > TOTAL_SUPPLY) {
            revert MaxSupply();
        }
        _safeMint(recipient, newTokenId);
        return newTokenId;
    }

    function tokenURI(uint256 tokenId)
        public
        view
        virtual
        override
        returns (string memory)
    {
        if (ownerOf(tokenId) == address(0)) {
            revert NonExistentTokenURI();
        }
        return
            bytes(baseURI).length > 0
                ? string(abi.encodePacked(baseURI, tokenId.toString()))
                : "";
    }

    function withdrawPayments(address payable payee) external onlyOwner {
        uint256 balance = address(this).balance;
        (bool transferTx, ) = payee.call{value: balance}("");
        if (!transferTx) {
            revert WithdrawTransfer();
        }
    }
}

Now, let’s try compiling our contract to make sure everything is in order.

forge build

If your output looks like this, the contracts successfully compiled. compile successful

Deploying our contract

We’re going to deploy the NFT contract to the Goerli testnet, but to do this we’ll need to configure Foundry a bit, by setting things like a Goerli RPC URL, the private key of an account that’s funded with Goerli Eth, and an Etherscan key for the verification of the NFT contract.

💡 Note: You can get some Goerli testnet ETH here .

Environment Configuration

Once you have all that create a .env file and add the variables. Foundry automatically loads in a .env file present in your project directory.

The .env file should follow this format:

GOERLI_RPC_URL=
PRIVATE_KEY=
ETHERSCAN_API_KEY=

We now need to edit the foundry.toml file. There should already be one in the root of the project.

Add the following lines to the end of the file:

[rpc_endpoints]
goerli = "${GOERLI_RPC_URL}"

[etherscan]
goerli = { key = "${ETHERSCAN_API_KEY}" }

This creates a RPC alias for Goerli and loads the Etherscan API key.

Writing the Script

Next, we have to create a folder and name it script and create a file in it called NFT.s.sol. This is where we will create the deployment script itself.

The contents of NFT.s.sol should look like this:

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.13;

import "forge-std/Script.sol";
import "../src/NFT.sol";

contract MyScript is Script {
    function run() external {
        uint256 deployerPrivateKey = vm.envUint("PRIVATE_KEY");
        vm.startBroadcast(deployerPrivateKey);

        NFT nft = new NFT("NFT_tutorial", "TUT", "baseUri");

        vm.stopBroadcast();
    }
}

Now let’s read through the code and figure out what it actually means and does.

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.13;

Remember even if it’s a script it still works like a smart contract, but is never deployed, so just like any other smart contract written in Solidity the pragma version has to be specified.

import "forge-std/Script.sol";
import "../src/NFT.sol";

Just like we may import Forge Std to get testing utilities when writing tests, Forge Std also provides some scripting utilities that we import here.

The next line just imports the NFT contract.

contract MyScript is Script {

We create a contract called MyScript and it inherits Script from Forge Std.

function run() external {

By default, scripts are executed by calling the function named run, our entrypoint.

uint256 deployerPrivateKey = vm.envUint("PRIVATE_KEY");

This loads in the private key from our .env file. Note: you must be careful when exposing private keys in a .env file and loading them into programs. This is only recommended for use with non-privileged deployers or for local / test setups. For production setups please review the various wallet options that Foundry supports.

vm.startBroadcast(deployerPrivateKey);

This is a special cheatcode that records calls and contract creations made by our main script contract. We pass the deployerPrivateKey in order to instruct it to use that key for signing the transactions. Later, we will broadcast these transactions to deploy our NFT contract.

NFT nft = new NFT("NFT_tutorial", "TUT", "baseUri");

Here we just create our NFT contract. Because we called vm.startBroadcast() before this line, the contract creation will be recorded by Forge, and as mentioned previously, we can broadcast the transaction to deploy the contract on-chain. The broadcast transaction logs will be stored in the broadcast directory by default. You can change the logs location by setting broadcast in your foundry.toml file.

Now that you’re up to speed about what the script smart contract does, let’s run it.

You should have added the variables we mentioned earlier to the .env for this next part to work.

At the root of the project run:

# To load the variables in the .env file
source .env

# To deploy and verify our contract
forge script script/NFT.s.sol:MyScript --rpc-url $GOERLI_RPC_URL --broadcast --verify -vvvv

Forge is going to run our script and broadcast the transactions for us - this can take a little while, since Forge will also wait for the transaction receipts. You should see something like this after a minute or so:

contract verified

This confirms that you have successfully deployed the NFT contract to the Goerli testnet and have also verified it on Etherscan, all with one command.

Deploying locally

You can deploy to Anvil, the local testnet, by configuring the port as the fork-url.

Here, we have two options in terms of accounts. We can either start anvil without any flags and use one of the private keys provided. Or, we can pass a mnemonic to anvil to use.

Using Anvil's Default Accounts

First, start Anvil:

anvil

Update your .env file with a private key given to you by Anvil.

Then run the following script:

forge script script/NFT.s.sol:MyScript --fork-url http://localhost:8545 --broadcast

Using a Custom Mnemonic

Add the following line to your .env file and complete it with your mnemonic:

MNEMONIC=

It is expected that the PRIVATE_KEY environment variable we set earlier is one of the first 10 accounts in this mnemonic.

Start Anvil with the custom mnemonic:

source .env

anvil -m $MNEMONIC

Then run the following script:

forge script script/NFT.s.sol:MyScript --fork-url http://localhost:8545 --broadcast

💡 Note: A full implementation of this tutorial can be found here and for further reading about solidity scripting, you can check out the forge script reference.

Forking Mainnet with Cast and Anvil

Introduction

By combining Anvil and Cast, you can fork and test by interacting with contracts on a real network. The goal of this tutorial is to show you how to transfer Dai tokens from someone who holds Dai to an account created by Anvil.

Set Up

Let's start by forking mainnet.

anvil --fork-url https://mainnet.infura.io/v3/$INFURA_KEY

You will see 10 accounts are created with their public and private keys. We will work with 0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266 (Let's call this user Alice).

Transferring Dai

Go to Etherscan and search for holders of Dai tokens (here). Let's pick a random account. In this example we will be using 0xad0135af20fa82e106607257143d0060a7eb5cbf. Let's export our contracts and accounts as environment variables:

export ALICE=0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
export DAI=0x6b175474e89094c44da98b954eedeac495271d0f
export LUCKY_USER=0xad0135af20fa82e106607257143d0060a7eb5cbf

We can check Alice's balance using cast call:

$ cast call $DAI \
  "balanceOf(address)(uint256)" \
  $ALICE
0

Similarly, we can also check our lucky user's balance using cast call:

$ cast call $DAI \
  "balanceOf(address)(uint256)" \
  $LUCKY_USER
71686045944718512103110072

Let's transfer some tokens from the lucky user to Alice using cast send:

# This calls Anvil and lets us impersonate our lucky user
$ cast rpc anvil_impersonateAccount $LUCKY_USER
$ cast send $DAI \
--unlocked \
--from $LUCKY_USER \
  "transfer(address,uint256)(bool)" \
  $ALICE \
  1686045944718512103110072
blockHash               0xbf31c45f6935a0714bb4f709b5e3850ab0cc2f8bffe895fefb653d154e0aa062
blockNumber             15052891
...

Let's check that the transfer worked:

cast call $DAI \
  "balanceOf(address)(uint256)" \
  $ALICE
1686045944718512103110072

$ cast call $DAI \
  "balanceOf(address)(uint256)" \
  $LUCKY_USER
70000000000000000000000000

Foundry Tutorials (Unofficial) Videos

Unofficial youtube playlists of Foundry tutorials from Blockchain educators.

URL	Description	Author
	Blockchain Developer, Solidity, Foundry Full Course 2023 ~ Learn Solidity, Blockchain Development, & Smart Contracts Powered By AI - Full Course	Patrick Collins
	Foundry ~ Playlist of beginner level videos on Foundry	Smart Contract Programmer

FAQ

This is a collection of common questions and answers. If you do not find your question listed here, hop in the Telegram support channel and let us help you!

`libusb` Error When Running `forge`/`cast`

If you are using the binaries as released, you may see the following error on MacOS:

dyld: Library not loaded: /usr/local/opt/libusb/lib/libusb-1.0.0.dylib

In order to fix this, you must install the libusb library:

brew install libusb

Out of Date `GLIBC` Error:

If you run into an error resembling the following after using foundryup:

forge: /lib/x86_64-linux-gnu/libc.so.6: version 'GLIBC_2.29' not found (required by forge)

There are 2 workarounds:

Help! I can't see my logs

Forge does not display logs by default. If you want to see logs from Hardhat's console.log or from DSTest-style log_* events, you need to run forge test with verbosity 2 (-vv).

If you want to see other events your contracts emit, you need to run with traces enabled. To do that, set the verbosity to 3 (-vvv) to see traces for failing tests, or 4 (-vvvv) to see traces for all tests.

My tests are failing and I don't know why

To gain better insight into why your tests are failing, try using traces. To enable traces, you need to increase the verbosity on forge test to at least 3 (-vvv) but you can go as high as 5 (-vvvvv) for even more traces.

You can learn more about traces in our Understanding Traces chapter.

How do I use `console.log`?

To use Hardhat's console.log you must add it to your project by copying the file over from here.

Alternatively, you can use Forge Std which comes bundled with console.log. To use console.log from Forge Std, you have to import it:

import "forge-std/console.sol";

How do I run specific tests?

If you want to run only a few tests, you can use --match-test to filter test functions, --match-contract to filter test contracts, and --match-path to filter test files on forge test.

How do I use a specific Solidity compiler?

Forge will try to auto-detect what Solidity compiler works for your project.

To use a specific Solidity compiler, you can set solc in your config file, or pass --use solc:<version> to a Forge command that supports it (e.g. forge build or forge test). Paths to a solc binary are also accepted. To use a specific local solc binary, you can set solc = "<path to solc>" in your config file, or pass --use "<path to solc>". The solc version/path can also be set via the env variable FOUNDRY_SOLC=<version/path>, but the cli arg --use has priority.

For example, if you have a project that supports all 0.7.x Solidity versions, but you want to compile with solc 0.7.0, you could use forge build --use solc:0.7.0.

How do I fork from a live network?

To fork from a live network, pass --fork-url <URL> to forge test. You can also fork from a specific block using --fork-block-number <BLOCK>, which adds determinism to your test, and allows Forge to cache the chain data for that block.

For example, to fork from Ethereum mainnet at block 10,000,000 you could use: forge test --fork-url $MAINNET_RPC_URL --fork-block-number 10000000.

How do I add my own assertions?

You can add your own assertions by creating your own base test contract and having that inherit from the test framework of your choice.

For example, if you use DSTest, you could create a base test contract like this:

contract TestBase is DSTest {
    function myCustomAssertion(uint a, uint b) {
      if (a != b) {
          emit log_string("a and b did not match");
          fail();
      }
    }
}

You would then inherit from TestBase in your test contracts.

contract MyContractTest is TestBase {
    function testSomething() {
        // ...
    }
}

Similarly, if you use Forge Std, you can create a base test contract that inherits from Test.

For a good example of a base test contract that has helper methods and custom assertions, see Solmate's DSTestPlus.

How do I use Forge offline?

Forge will sometimes check for newer Solidity versions that fit your project. To use Forge offline, use the --offline flag.

I'm getting Solc errors

solc-bin doesn't offer static builds for apple silicon. Foundry relies on svm to install native builds for apple silicon.

All solc versions are installed under ~/.svm/. If you encounter solc related errors, such as SolcError: ... please to nuke ~/.svm/ and try again, this will trigger a fresh install and usually resolves the issue.

If you're on apple silicon, please ensure the z3 theorem prover is installed: brew install z3

Note: native apple silicon builds are only available from 0.8.5 upwards. If you need older versions, you must enable apple silicon rosetta to run them.

Forge fails in JavaScript monorepos (`pnpm`)

Managers like pnpm use symlinks to manage node_modules folders.

A common layout may look like:

├── contracts
│    ├── contracts
│    ├── foundry.toml
│    ├── lib
│    ├── node_modules
│    ├── package.json
├── node_modules
│    ├── ...
├── package.json
├── pnpm-lock.yaml
├── pnpm-workspace.yaml

Where the Foundry workspace is in ./contracts, but packages in ./contracts/node_modules are symlinked to ./node_modules.

When running forge build in ./contracts/node_modules, this can lead to an error like:

error[6275]: ParserError: Source "node_modules/@openzeppelin/contracts/utils/cryptography/draft-EIP712.sol" not found: File outside of allowed directories. The following are allowed: "<repo>/contracts", "<repo>/contracts/contracts", "<repo>/contracts/lib".
 --> node_modules/@openzeppelin/contracts/token/ERC20/extensions/draft-ERC20Permit.sol:8:1:
  |
8 | import "../../../utils/cryptography/draft-EIP712.sol";

This error happens when solc was able to resolve symlinked files, but they're outside the Foundry workspace (./contracts).

Adding node_modules to allow_paths in foundry.toml grants solc access to that directory, and it will be able to read it:

# This translates to `solc --allow-paths ../node_modules`
allow_paths = ["../node_modules"]

Note that the path is relative to the Foundry workspace. See also solc allowed-paths

I'm getting `Permission denied (os error 13)`

If you see an error like

Failed to create artifact parent folder "/.../MyProject/out/IsolationModeMagic.sol": Permission denied (os error 13)

Then there's likely a folder permission issue. Ensure user has write access in the project root's folder.

It has been reported that on linux, canonicalizing paths can result in weird paths (/_1/...). This can be resolved by nuking the entire project folder and initializing again.

Connection refused when run `forge build` .

If you're unable to access github URLs called by forge build, you will see an error like

Error:
error sending request for url (https://raw.githubusercontent.com/roynalnaruto/solc-builds/ff4ea8a7bbde4488428de69f2c40a7fc56184f5e/macosx/aarch64/list.json): error trying to connect: tcp connect error: Connection refused (os error 61)

Connection failed because access to the URL from your location may be restricted. To solve this, you should set proxy.

You could run export http_proxy=http://127.0.0.1:7890 https_proxy=http://127.0.0.1:7890 first in the terminal then you will forge build successfully.

Contributing

Thanks for your interest in improving Foundry!

There are multiple opportunities to contribute at any level. It doesn't matter if you are just getting started with Rust or are the most weathered expert, we can use your help.

No contribution is too small and all contributions are valued.

This document will help you get started. Do not let the document intimidate you. It should be considered as a guide to help you navigate the process.

The dev Telegram is available for any concerns you may have that are not covered in this guide.

First check the Contribution guidelines

Some articles to walk you through the first steps:

References

forge Commands

General Commands

forge

NAME

forge - Build, test, fuzz, debug and deploy Solidity contracts.

SYNOPSIS

forge [options] command [args]
forge [options] --version
forge [options] --help

DESCRIPTION

This program is a set of tools to build, test, fuzz, debug and deploy Solidity smart contracts.

COMMANDS

General Commands

forge help
Display help information about Forge.

forge completions
Generate shell autocompletions for Forge.

Project Commands

forge init
Create a new Forge project.

forge install
Install one or multiple dependencies.

forge update
Update one or multiple dependencies.

forge remove
Remove one or multiple dependencies.

forge config
Display the current config.

forge remappings
Get the automatically inferred remappings for this project.

forge tree
Display a tree visualization of the project's dependency graph.

forge geiger Detects usage of unsafe cheat codes in a foundry project and its dependencies.

Build Commands

forge build
Build the project's smart contracts.

forge clean
Remove the build artifacts and cache directories.

forge inspect
Get specialized information about a smart contract.

Test Commands

forge test
Run the project's tests.

forge snapshot
Create a snapshot of each test's gas usage.

Deploy Commands

forge create
Deploy a smart contract.

forge verify-contract
Verify smart contracts on Etherscan.

forge verify-check
Check verification status on Etherscan.

forge flatten
Flatten a source file and all of its imports into one file.

Utility Commands

forge debug
Debug a single smart contract as a script.

forge bind
Generate Rust bindings for smart contracts.

forge cache
Manage the Foundry cache.

forge cache clean
Cleans cached data from ~/.foundry.

forge cache ls
Shows cached data from ~/.foundry.

forge script
Run a smart contract as a script, building transactions that can be sent onchain.

forge upload-selectors
Uploads abi of given contract to https://sig.eth.samczsun.com function selector database.

forge doc
Generate documentation for Solidity source files.

OPTIONS

Special Options

-V
--version
Print version info and exit.

Common Options

-h
--help
Prints help information.

FILES

~/.foundry/
Default location for Foundry's "home" directory where it stores various files.

~/.foundry/bin/
Binaries installed using foundryup will be located here.

~/.foundry/cache/
Forge's cache directory, where it stores cached block data and more.

~/.foundry/foundry.toml
The global Foundry config.

~/.svm
The location of the Forge-managed solc binaries.

EXAMPLES

Create a new Forge project:
```
forge init hello_foundry
```
Build a project:
```
forge build
```
Run a project's tests:
```
forge test
```

BUGS

See https://github.com/foundry-rs/foundry/issues for issues.

forge help

NAME

forge-help - Get help for a Forge command

SYNOPSIS

forge help [subcommand]

DESCRIPTION

Prints a help message for the given command.

EXAMPLES

Get help for a command:
```
forge help build
```
Help is also available with the --help flag:
```
forge build --help
```

forge completions

NAME

forge-completions - Generate shell completions script

SYNOPSIS

forge completions shell

DESCRIPTION

Generates a shell completions script for the given shell.

Supported shells are:

bash
elvish
fish
powershell
zsh

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Generate shell completions script for zsh:

forge completions zsh > $HOME/.oh-my-zsh/completions/_forge

Project Commands

forge init

NAME

forge-init - Create a new Forge project.

SYNOPSIS

forge init [options] [root]

DESCRIPTION

Create a new Forge project in the directory root (by default the current working directory).

The default template creates the following project layout:

.
├── foundry.toml
├── lib
│   └── forge-std
│       ├── LICENSE-APACHE
│       ├── LICENSE-MIT
│       ├── README.md
│       ├── foundry.toml
│       ├── lib
│       └── src
├── script
│   └── Counter.s.sol
├── src
│   └── Counter.sol
└── test
    └── Counter.t.sol

7 directories, 8 files

However, it is possible to create a project from another using --template.

By default, forge init will also initialize a new git repository, install some submodules and create an initial commit message.

If you do not want this behavior, pass --no-git.

OPTIONS

Init Options

--force
Create the project even if the specified root directory is not empty.

-t template
--template template
The template to start from.

--vscode
Create a .vscode/settings.json file with Solidity settings, and generate a remappings.txt file.

--offline
Do not install dependencies from the network.

VCS Options

--no-commit
Do not create an initial commit.

--no-git
Do not create a git repository.

Display Options

-q
--quiet
Do not print any messages.

Common Options

-h
--help
Prints help information.

EXAMPLES

Create a new project:
```
forge init hello_foundry
```
Create a new project, but do not create a git repository:
```
forge init --no-git hello_foundry
```
Forcibly create a new project in a non-empty directory:
```
forge init --force 
```

forge install

NAME

forge-install - Install one or more dependencies.

SYNOPSIS

forge install [options] [deps...]

DESCRIPTION

Install one or more dependencies.

Dependencies are installed as git submodules. If you do not want this behavior, pass --no-git.

If no arguments are provided, then existing dependencies are installed.

Dependencies can be a raw URL (https://foo.com/dep), an SSH URL (git@github.com:owner/repo), or the path to a GitHub repository (owner/repo). Additionally, a ref can be added to the dependency path to install a specific version of a dependency.

A ref can be:

A branch: owner/repo@master
A tag: owner/repo@v1.2.3
A commit: owner/repo@8e8128

The ref defaults to master.

You can also choose the name of the folder the dependency will be in. By default, the folder name is the name of the repository. If you want to change the name of the folder, prepend <folder>= to the dependency.

OPTIONS

Project Options

--root path
The project's root path. By default, this is the root directory of the current git repository, or the current working directory.

VCS Options

--no-commit
Do not create a commit.

--no-git
Install without adding the dependency as a submodule.

Display Options

-q
--quiet
Do not print any messages.

Common Options

-h
--help
Prints help information.

EXAMPLES

Install a dependency:
```
forge install transmissions11/solmate
```
Install a specific version of a dependency:
```
forge install transmissions11/solmate@v7
```

Install multiple dependencies:

forge install transmissions11/solmate@v7 OpenZeppelin/openzeppelin-contracts

Install a dependency without creating a submodule:
```
forge install --no-git transmissions11/solmate
```

Install a dependency in a specific folder:

forge install soulmate=transmissions11/solmate

forge update

NAME

forge-update - Update one or more dependencies.

SYNOPSIS

forge update [options] [dep]

DESCRIPTION

Update one or more dependencies.

The argument dep is a path to the dependency you want to update. Forge will update to the latest version on the ref you specified for the dependency when you ran forge install.

If no argument is provided, then all dependencies are updated.

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Update a dependency:
```
forge update lib/solmate
```
Update all dependencies:
```
forge update
```

forge remove

NAME

forge-remove - Remove one or multiple dependencies.

SYNOPSIS

forge remove [options] [deps...]

DESCRIPTION

Remove one or multiple dependencies.

Dependencies can be a raw URL (https://foo.com/dep), the path to a GitHub repository (owner/repo) or the path to the dependency in the project tree.

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Remove a dependency by path:
```
forge remove lib/solmate
```
Remove a dependency by GitHub repository name:
```
forge remove dapphub/solmate
```

forge config

NAME

forge-config - Display the current config.

SYNOPSIS

forge config [options]

DESCRIPTION

Display the current config.

This command can be used to create a new basic foundry.toml or to see what values are currently set, taking environment variables and the global configuration file into account.

The command supports almost all flags of the other commands in Forge to allow overriding values in the displayed configuration.

OPTIONS

Config Options

--basic
Prints a basic configuration file.

--fix
Attempts to fix any configuration warnings.

Common Options

-h
--help
Prints help information.

EXAMPLES

Create a new basic config:
```
forge config > foundry.toml
```
Enable FFI in foundry.toml:
```
forge config --ffi > foundry.toml
```

forge remappings

NAME

forge-remappings - Get the automatically inferred remappings for the project.

SYNOPSIS

forge remappings [options]

DESCRIPTION

Get the automatically inferred remappings for the project.

OPTIONS

Project Options

--root path
The project's root path. By default, this is the root directory of the current git repository, or the current working directory.

--lib-path path
The path to the library folder.

Common Options

-h
--help
Prints help information.

EXAMPLES

Create a remappings.txt file from the inferred remappings:
```
forge remappings > remappings.txt
```

forge tree

NAME

forge-tree - Display a tree visualization of the project's dependency graph.

SYNOPSIS

forge tree [options]

DESCRIPTION

Display a visualization of the project's dependency graph.

$ forge tree
src/OpenZeppelinNft.sol 0.8.10
├── lib/openzeppelin-contracts/contracts/token/ERC721/ERC721.sol ^0.8.0
│   ├── lib/openzeppelin-contracts/contracts/token/ERC721/IERC721.sol ^0.8.0
│   │   └── lib/openzeppelin-contracts/contracts/utils/introspection/IERC165.sol ^0.8.0
│   ├── lib/openzeppelin-contracts/contracts/token/ERC721/IERC721Receiver.sol ^0.8.0
│   ├── lib/openzeppelin-contracts/contracts/token/ERC721/extensions/IERC721Metadata.sol ^0.8.0
│   │   └── lib/openzeppelin-contracts/contracts/token/ERC721/IERC721.sol ^0.8.0 (*)
│   ├── lib/openzeppelin-contracts/contracts/utils/Address.sol ^0.8.1
│   ├── lib/openzeppelin-contracts/contracts/utils/Context.sol ^0.8.0
│   ├── lib/openzeppelin-contracts/contracts/utils/Strings.sol ^0.8.0
│   └── lib/openzeppelin-contracts/contracts/utils/introspection/ERC165.sol ^0.8.0
│       └── lib/openzeppelin-contracts/contracts/utils/introspection/IERC165.sol ^0.8.0
├── lib/openzeppelin-contracts/contracts/utils/Strings.sol ^0.8.0
├── lib/openzeppelin-contracts/contracts/security/PullPayment.sol ^0.8.0
│   └── lib/openzeppelin-contracts/contracts/utils/escrow/Escrow.sol ^0.8.0
│       ├── lib/openzeppelin-contracts/contracts/access/Ownable.sol ^0.8.0
│       │   └── lib/openzeppelin-contracts/contracts/utils/Context.sol ^0.8.0
│       └── lib/openzeppelin-contracts/contracts/utils/Address.sol ^0.8.1
└── lib/openzeppelin-contracts/contracts/access/Ownable.sol ^0.8.0 (*)
src/SolmateNft.sol 0.8.10
├── lib/solmate/src/tokens/ERC721.sol >=0.8.0
├── lib/openzeppelin-contracts/contracts/utils/Strings.sol ^0.8.0
├── lib/openzeppelin-contracts/contracts/security/PullPayment.sol ^0.8.0 (*)
└── lib/openzeppelin-contracts/contracts/access/Ownable.sol ^0.8.0 (*)
test/OpenZeppelinNft.t.sol 0.8.10
├── lib/forge-std/src/Test.sol >=0.6.0 <0.9.0
│   ├── lib/forge-std/src/Script.sol >=0.6.0 <0.9.0
│   │   ├── lib/forge-std/src/Vm.sol >=0.6.0
│   │   ├── lib/forge-std/src/console.sol >=0.4.22 <0.9.0
│   │   └── lib/forge-std/src/console2.sol >=0.4.22 <0.9.0
│   └── lib/forge-std/lib/ds-test/src/test.sol >=0.5.0
├── src/OpenZeppelinNft.sol 0.8.10 (*)
└── lib/openzeppelin-contracts/contracts/token/ERC721/IERC721Receiver.sol ^0.8.0
test/SolmateNft.sol 0.8.10
├── lib/forge-std/src/Test.sol >=0.6.0 <0.9.0 (*)
└── src/SolmateNft.sol 0.8.10 (*)

OPTIONS

Flatten Options

--charset charset
Character set to use in output: utf8, ascii. Default: utf8

--no-dedupe
Do not de-duplicate (repeats all shared dependencies)

Project Options

--build-info
Generate build info files.

--build-info-path path
Output path to directory that build info files will be written to.

--root path
The project's root path. By default, this is the root directory of the current git repository, or the current working directory.

-C path
--contracts path
The contracts source directory.
Environment: DAPP_SRC

--lib-paths path
The path to the library folder.

-R remappings
--remappings remappings
The project's remappings.

The parameter is a comma-separated list of remappings in the format <source>=<dest>.

--cache-path path
The path to the compiler cache.

--config-path file
Path to the config file.

--hh
--hardhat
This is a convenience flag, and is the same as passing --contracts contracts --lib-paths node-modules.

Common Options

-h
--help
Prints help information.

forge geiger

NAME

forge-geiger - Detects usage of unsafe cheat codes in a foundry project and its dependencies.

SYNOPSIS

forge geiger [options] [path]

DESCRIPTION

Detects usage of unsafe cheat codes in a foundry project and its dependencies.

OPTIONS

--root path
The project's root path. By default, this is the root directory of the current git repository, or the current working directory.

--check
Run in 'check' mode. Exits with 0 if no unsafe cheat codes were found. Exits with 1 if unsafe cheat codes are detected.

--full
Print a full report of all files even if no unsafe functions are found.

Common Options

-h
--help
Prints help information.

Build Commands

forge build

NAME

forge-build - Build the project's smart contracts.

SYNOPSIS

forge build or forge b [options]

DESCRIPTION

Build the project's smart contracts.

The command will try to detect the latest version that can compile your project by looking at the version requirements of all your contracts and dependencies.

You can override this behaviour by passing --no-auto-detect. Alternatively, you can pass --use <SOLC_VERSION>.

If the command detects that the Solidity compiler version it is using to build is not installed, it will download it and install it in ~/.svm. You can disable this behavior by passing --offline.

The build is incremental, and the build cache is saved in cache/ in the project root by default. If you want to clear the cache, pass --force, and if you want to change the cache directory, pass --cache-path <PATH>.

Build Modes

There are three build modes:

Just compilation (default): Builds the project and saves the contract artifacts in out/ (or the path specified by --out <PATH>).
Size mode (--sizes): Builds the project, displays the size of non-test contracts and exits with code 1 if any of them are above the size limit.
Name mode (--names): Builds the project, displays the names of the contracts and exits.

The Optimizer

You can enable the optimizer by passing --optimize, and you can adjust the number of optimizer runs by passing --optimizer-runs <RUNS>.

You can also opt-in to the Solidity IR compilation pipeline by passing --via-ir. Read more about the IR pipeline in the Solidity docs.

By default, the optimizer is enabled and runs for 200 cycles.

Conditional Optimizer Usage

Many projects use the solc optimizer, either through the standard compilation pipeline or the IR pipeline. But in some cases, the optimizer can significantly slow down compilation speeds.

A config file for a project using the optimizer may look like this for regular compilation:

[profile.default]
solc-version = "0.8.17"
optimizer = true
optimizer-runs = 10_000_000

Or like this for via-ir:

[profile.default]
solc-version = "0.8.17"
via_ir = true

To reduce compilation speeds during development and testing, one approach is to have a lite profile that has the optimizer off and use this for development/testing cycle. The updated config file for regular compilation may look like this:

[profile.default]
solc-version = "0.8.17"
optimizer = true
optimizer-runs = 10_000_000

[profile.lite]
optimizer = false

Or like this for via-ir:

[profile.default]
solc-version = "0.8.17"
via_ir = true

[profile.lite.optimizer_details.yulDetails]
optimizerSteps = ''

When setup like this, forge build (or forge test / forge script) still uses the standard profile, so by default a forge script invocation will deploy your contracts with the production setting. Running FOUNDRY_PROFILE=lite forge build (and again, same for the test and script commands) will use the lite profile to reduce compilation times.

There are additional optimizer details you can configure, see the Additional Optimizer Settings section below for more info.

Artifacts

You can add extra output from the Solidity compiler to your artifacts by passing --extra-output <SELECTOR>.

The selector is a path in the Solidity compiler output, which you can read more about in the Solidity docs.

You can also write some of the compiler output to separate files by passing --extra-output-files <SELECTOR>.

Valid selectors for --extra-output-files are:

metadata: Written as a metadata.json file in the artifacts directory
ir: Written as a .ir file in the artifacts directory
irOptimized: Written as a .iropt file in the artifacts directory
ewasm: Written as a .ewasm file in the artifacts directory
evm.assembly: Written as a .asm file in the artifacts directory

Watch Mode

The command can be run in watch mode by passing --watch [PATH...], which will rebuild every time a watched file or directory is changed. The source directory is watched by default.

Sparse Mode (experimental)

Sparse mode only compiles files that match certain criteria.

By default, this filter applies to files that have not been changed since the last build, but for commands that take file filters (e.g. forge test), sparse mode will only recompile files that match the filter.

Sparse mode is opt-in until the feature is stabilized. To opt-in to sparse mode and try it out, set sparse_mode in your configuration file.

Additional Optimizer Settings

The optimizer can be fine-tuned with additional settings. Simply set the optimizer_details table in your configuration file. For example:

[profile.default.optimizer_details]
constantOptimizer = true
yul = true

[profile.default.optimizer_details.yulDetails]
stackAllocation = true
optimizerSteps = 'dhfoDgvulfnTUtnIf'

See the compiler input description documentation for more information on available settings (specifically settings.optimizer.details).

Revert Strings

You can control how revert strings are generated by the compiler. By default, only user supplied revert strings are included in the bytecode, but there are other options:

strip: Removes all revert strings (if possible, i.e. if literals are used) keeping side-effects.
debug: Injects strings for compiler-generated internal reverts, implemented for ABI encoders V1 and V2 for now.
verboseDebug: Appends further information to user-supplied revert strings (not yet implemented).

Additional Model Checker settings

Solidity's built-in model checker is an opt-in module that can be enabled via the ModelChecker object.

See Compiler Input Description settings.modelChecker and the model checker's options.

The module is available in solc release binaries for OSX and Linux. The latter requires the z3 library version [4.8.8, 4.8.14] to be installed in the system (SO version 4.8).

Similarly to the optimizer settings above, the model_checker settings must be prefixed with the profile they correspond to: [profile.default.model_checker] belongs to the [profile.default].

## foundry.toml
[profile.default.model_checker]
contracts = { '/path/to/project/src/Contract.sol' = [ 'Contract' ] }
engine = 'chc'
timeout = 10000
targets = [ 'assert' ]

The fields above are recommended when using the model checker. Setting which contract should be verified is extremely important, otherwise all available contracts will be verified which can consume a lot of time. The recommended engine is chc, but bmc and all (runs both) are also accepted. It is also important to set a proper timeout (given in milliseconds), since the default time given to the underlying solvers may not be enough. If no verification targets are given, only assertions will be checked.

The model checker will run when forge build is invoked, and will show findings as warnings if any.

OPTIONS

Build Options

--names Print compiled contract names.

--sizes Print compiled non-test contract sizes, exiting with code 1 if any of them are above the size limit.

--skip Skip compilation of non-essential contract directories like test or script (usage --skip test).

Cache Options

--force
Clear the cache and artifacts folder and recompile.

Linker Options

--libraries libraries
Set pre-linked libraries.

The parameter must be in the format <remapped path to lib>:<library name>:<address>, e.g. src/Contract.sol:Library:0x....

Can also be set in your configuration file as libraries = ["<path>:<lib name>:<address>"].

Compiler Options

--optimize
Activate the Solidity optimizer.

--optimizer-runs runs
The number of optimizer runs.

--via-ir
Use the Yul intermediate representation compilation pipeline.

--revert-strings
How to treat revert and require reason strings.

--use solc_version
Specify the solc version, or a path to a local solc, to build with.

Valid values are in the format x.y.z, solc:x.y.z or path/to/solc.

--offline
Do not access the network. Missing solc versions will not be installed.

--no-auto-detect
Do not auto-detect solc.

--ignored-error-codes error_codes
Ignore solc warnings by error code. The parameter is a comma-separated list of error codes.

--extra-output selector
Extra output to include in the contract's artifact.

Example keys: abi, storageLayout, evm.assembly, ewasm, ir, ir-optimized, metadata.

For a full description, see the Solidity docs.

--extra-output-files selector
Extra output to write to separate files.

Example keys: abi, storageLayout, evm.assembly, ewasm, ir, ir-optimized, metadata.

For a full description, see the Solidity docs.

--evm-version version
The target EVM version.

Project Options

--build-info
Generate build info files.

--build-info-path path
Output path to directory that build info files will be written to.

--root path
The project's root path. By default, this is the root directory of the current git repository, or the current working directory.

-C path
--contracts path
The contracts source directory.
Environment: DAPP_SRC

--lib-paths path
The path to the library folder.

-R remappings
--remappings remappings
The project's remappings.

The parameter is a comma-separated list of remappings in the format <source>=<dest>.

--cache-path path
The path to the compiler cache.

--config-path file
Path to the config file.

--hh
--hardhat
This is a convenience flag, and is the same as passing --contracts contracts --lib-paths node-modules.

-o path
--out path
The project's artifacts directory.

--silent
Suppress all output.

Watch Options

-w [path...]
--watch [path...]
Watch specific file(s) or folder(s).

By default, the project's source directory is watched.

-d delay
--delay delay
File update debounce delay.

During the delay, incoming change events are accumulated and only once the delay has passed, is an action taken.
Note that this does not mean a command will be started: if --no-restart is given and a command is already running, the outcome of the action will be to do nothing.

Defaults to 50ms. Parses as decimal seconds by default, but using an integer with the ms suffix may be more convenient.

When using --poll mode, you'll want a larger duration, or risk overloading disk I/O.

--no-restart
Do not restart the command while it's running.

--run-all
Explicitly re-run the command on all files when a change is made.

Common Options

-h
--help
Prints help information.

EXAMPLES

Build the project:
```
forge build
```
Build the project with solc 0.6.0:
```
forge build --use solc:0.6.0
```
Build the project with additional artifact output:
```
forge build --extra-output evm.assembly
```
Build the project in watch mode:
```
forge build --watch
```

forge clean

NAME

forge-clean - Remove the build artifacts and cache directories.

SYNOPSIS

forge clean [options]

DESCRIPTION

Remove the build artifacts and cache directories.

OPTIONS

Clean Options

--root path
The project's root path. Defaults to the current working directory.

Common Options

-h
--help
Prints help information.

EXAMPLES

Clean artifacts and cache in a project:
```
forge clean
```

forge inspect

NAME

forge-inspect - Get specialized information about a smart contract

SYNOPSIS

forge inspect [options] contract_name field

DESCRIPTION

Get specialized information about a smart contract.

The field to inspect (field) can be any of:

abi
b/bytes/bytecode
deployedBytecode/deployed_bytecode/deployed-bytecode/deployedbytecode/deployed
assembly/asm
asmOptimized/assemblyOptimized/assemblyoptimized/assembly_optimized/asmopt/assembly-optimized/asmo/asm-optimized/asmoptimized/asm_optimized
methods/methodidentifiers/methodIdentifiers/method_identifiers/method-identifiers/mi
gasEstimates/gas/gas_estimates/gas-estimates/gasestimates
storageLayout/storage_layout/storage-layout/storagelayout/storage
devdoc/dev-doc/devDoc
ir
ir-optimized/irOptimized/iroptimized/iro/iropt
metadata/meta
userdoc/userDoc/user-doc
ewasm/e-wasm

OPTIONS

--pretty
Pretty print the selected field, if supported.

Cache Options

--force
Clear the cache and artifacts folder and recompile.

Linker Options

--libraries libraries
Set pre-linked libraries.

The parameter must be in the format <remapped path to lib>:<library name>:<address>, e.g. src/Contract.sol:Library:0x....

Can also be set in your configuration file as libraries = ["<path>:<lib name>:<address>"].

Compiler Options

--optimize
Activate the Solidity optimizer.

--optimizer-runs runs
The number of optimizer runs.

--via-ir
Use the Yul intermediate representation compilation pipeline.

--revert-strings
How to treat revert and require reason strings.

--use solc_version
Specify the solc version, or a path to a local solc, to build with.

Valid values are in the format x.y.z, solc:x.y.z or path/to/solc.

--offline
Do not access the network. Missing solc versions will not be installed.

--no-auto-detect
Do not auto-detect solc.

--ignored-error-codes error_codes
Ignore solc warnings by error code. The parameter is a comma-separated list of error codes.

--extra-output selector
Extra output to include in the contract's artifact.

Example keys: abi, storageLayout, evm.assembly, ewasm, ir, ir-optimized, metadata.

For a full description, see the Solidity docs.

--extra-output-files selector
Extra output to write to separate files.

Example keys: abi, storageLayout, evm.assembly, ewasm, ir, ir-optimized, metadata.

For a full description, see the Solidity docs.

--evm-version version
The target EVM version.

Project Options

--build-info
Generate build info files.

--build-info-path path
Output path to directory that build info files will be written to.

--root path
The project's root path. By default, this is the root directory of the current git repository, or the current working directory.

-C path
--contracts path
The contracts source directory.
Environment: DAPP_SRC

--lib-paths path
The path to the library folder.

-R remappings
--remappings remappings
The project's remappings.

The parameter is a comma-separated list of remappings in the format <source>=<dest>.

--cache-path path
The path to the compiler cache.

--config-path file
Path to the config file.

--hh
--hardhat
This is a convenience flag, and is the same as passing --contracts contracts --lib-paths node-modules.

-o path
--out path
The project's artifacts directory.

--silent
Suppress all output.

Common Options

-h
--help
Prints help information.

EXAMPLES

Inspect the bytecode of a contract:
```
forge inspect MyContract bytecode
```
Inspect the storage layout of a contract:
```
forge inspect MyContract storage
```

Test Commands

forge test

NAME

forge-test - Run the project's tests.

SYNOPSIS

forge test [options]

DESCRIPTION

Run the project's tests.

Forking

It is possible to run the tests in a forked environment by passing --fork-url <URL>.

When the tests are running in a forked environment, you can access all the state of the forked chain as you would if you had deployed the contracts. Cheatcodes are still available.

You can also specify a block number to fork from by passing --fork-block-number <BLOCK>. When forking from a specific block, the chain data is cached to ~/.foundry/cache. If you do not want to cache the chain data, pass --no-storage-caching.

Traces that cannot be decoded by local contracts when running in a forked environment (e.g. calls to contracts that live on mainnet, like tokens) can optionally be decoded using Etherscan. To use Etherscan for trace decoding, set ETHERSCAN_API_KEY or pass --etherscan-api-key <KEY>.

Debugging

It is possible to run a test in an interactive debugger. To start the debugger, pass --debug <TEST>.

If multiple tests match the specified pattern, you must use other test filters in order to reduce the matching number of tests to exactly 1.

If the test is a unit test, it is immediately opened in the debugger.

If the test is a fuzz test, the fuzz test is run and the debugger is opened on the first failing scenario. If there are no failing scenarios for the fuzz test, the debugger is opened on the last scenario.

More information on the debugger can be found in the debugger chapter.

Gas reports

You can generate a gas report by passing --gas-report.

More information on gas reports can be found in the gas reports chapter.

List

It is possible to list the tests without running them. You can pass --json to make it easier for outside extensions to parse structured content.

OPTIONS

Test Options

-m regex
--match regex
Only run test functions matching the specified regex pattern.
Deprecated: See --match-test.

--match-test regex
Only run test functions matching the specified regex pattern.

--no-match-test regex
Only run test functions that do not match the specified regex pattern.

--match-contract regex
Only run tests in contracts matching the specified regex pattern.

--no-match-contract regex
Only run tests in contracts that do not match the specified regex pattern.

--match-path glob
Only run tests in source files matching the specified glob pattern.

--no-match-path glob
Only run tests in source files that do not match the specified glob pattern.

--debug regex
Run a test in the debugger.

The argument passed to this flag is the name of the test function you want to run, and it works the same as --match-test.

If more than one test matches your specified criteria, you must add additional filters until only one test is found (see --match-contract and --match-path).

The matching test will be opened in the debugger regardless of the outcome of the test.

If the matching test is a fuzz test, then it will open the debugger on the first failure case. If the fuzz test does not fail, it will open the debugger on the last fuzz case.

For more fine-grained control of which fuzz case is run, see forge debug.

--gas-report
Print a gas report.

--allow-failure
Exit with code 0 even if a test fails.

--fail-fast
Stop running tests after the first failure.

--etherscan-api-key key
Etherscan API key. If set, traces are decoded using Etherscan if --fork-url is also set.
Environment: ETHERSCAN_API_KEY

EVM Options

-f url
--rpc-url url
--fork-url url
Fetch state over a remote endpoint instead of starting from an empty state.

If you want to fetch state from a specific block number, see --fork-block-number.

--fork-block-number block
Fetch state from a specific block number over a remote endpoint. See --fork-url.

--fork-retry-backoff <BACKOFF>
Initial retry backoff on encountering errors.

--no-storage-caching
Explicitly disables the use of RPC caching.

All storage slots are read entirely from the endpoint. See --fork-url.

-v
--verbosity
Verbosity of the EVM.

Pass multiple times to increase the verbosity (e.g. -v, -vv, -vvv).

    Verbosity levels:
    - 2: Print logs for all tests
    - 3: Print execution traces for failing tests
    - 4: Print execution traces for all tests, and setup traces for failing tests
    - 5: Print execution and setup traces for all tests

--sender address
The address which will be executing tests

--initial-balance balance
The initial balance of deployed contracts

--ffi
Enables the FFI cheatcode

Executor Options

--base-fee <FEE>
--block-base-fee-per-gas <FEE>
The base fee in a block (in wei).

--block-coinbase address
The coinbase of the block.

--block-difficulty difficulty
The block difficulty.

--block-gas-limit gas_limit
The block gas limit.

--block-number block
The block number.

--block-timestamp timestamp
The timestamp of the block (in seconds).

--chain-id chain_id
The chain ID.

--gas-limit gas_limit
The block gas limit.

--gas-price gas_price
The gas price (in wei).

--tx-origin address
The transaction origin.

Cache Options

--force
Clear the cache and artifacts folder and recompile.

Linker Options

--libraries libraries
Set pre-linked libraries.

The parameter must be in the format <remapped path to lib>:<library name>:<address>, e.g. src/Contract.sol:Library:0x....

Can also be set in your configuration file as libraries = ["<path>:<lib name>:<address>"].

Compiler Options

--optimize
Activate the Solidity optimizer.

--optimizer-runs runs
The number of optimizer runs.

--via-ir
Use the Yul intermediate representation compilation pipeline.

--revert-strings
How to treat revert and require reason strings.

--use solc_version
Specify the solc version, or a path to a local solc, to build with.

Valid values are in the format x.y.z, solc:x.y.z or path/to/solc.

--offline
Do not access the network. Missing solc versions will not be installed.

--no-auto-detect
Do not auto-detect solc.

--ignored-error-codes error_codes
Ignore solc warnings by error code. The parameter is a comma-separated list of error codes.

--extra-output selector
Extra output to include in the contract's artifact.

Example keys: abi, storageLayout, evm.assembly, ewasm, ir, ir-optimized, metadata.

For a full description, see the Solidity docs.

--extra-output-files selector
Extra output to write to separate files.

Example keys: abi, storageLayout, evm.assembly, ewasm, ir, ir-optimized, metadata.

For a full description, see the Solidity docs.

--evm-version version
The target EVM version.

Project Options

--build-info
Generate build info files.

--build-info-path path
Output path to directory that build info files will be written to.

--root path
The project's root path. By default, this is the root directory of the current git repository, or the current working directory.

-C path
--contracts path
The contracts source directory.
Environment: DAPP_SRC

--lib-paths path
The path to the library folder.

-R remappings
--remappings remappings
The project's remappings.

The parameter is a comma-separated list of remappings in the format <source>=<dest>.

--cache-path path
The path to the compiler cache.

--config-path file
Path to the config file.

--hh
--hardhat
This is a convenience flag, and is the same as passing --contracts contracts --lib-paths node-modules.

-o path
--out path
The project's artifacts directory.

--silent
Suppress all output.

Watch Options

-w [path...]
--watch [path...]
Watch specific file(s) or folder(s).

By default, the project's source directory is watched.

-d delay
--delay delay
File update debounce delay.

Defaults to 50ms. Parses as decimal seconds by default, but using an integer with the ms suffix may be more convenient.

When using --poll mode, you'll want a larger duration, or risk overloading disk I/O.

--no-restart
Do not restart the command while it's running.

--run-all
Explicitly re-run the command on all files when a change is made.

Display Options

-j
--json
Print the deployment information as JSON.

--list
List tests instead of running them.

Common Options

-h
--help
Prints help information.

EXAMPLES

Run the tests:
```
forge test
```
Open a test in the debugger:
```
forge test --debug testSomething
```
Generate a gas report:
```
forge test --gas-report
```

Only run tests in test/Contract.t.sol in the BigTest contract that start with testFail:

forge test --match-path test/Contract.t.sol --match-contract BigTest \
  --match-test "testFail*"

List tests in desired format

forge test --list
forge test --list --json
forge test --list --json --match-test "testFail*" | tail -n 1 | json_pp

forge snapshot

NAME

forge-snapshot - Create a snapshot of each test's gas usage.

SYNOPSIS

forge snapshot [options]

DESCRIPTION

Create a snapshot of each test's gas usage.

The results are written to a file named .gas-snapshot. You can change the name of the file by passing --snap <PATH>.

Fuzz tests are included by default in the snapshot. They use a static seed to achieve deterministic results.

Snapshots can be compared with --diff and --check. The first flag will output a diff, and the second will output a diff and exit with code 1 if the snapshots do not match.

OPTIONS

Snapshot Options

--asc
Sort results by gas used (ascending).

--desc
Sort results by gas used (descending).

--min min_gas
Only include tests that used more gas that the given amount.

--max max_gas
Only include tests that used less gas that the given amount.

--diff path
Output a diff against a pre-existing snapshot.

By default the comparison is done with .gas-snapshot.

--check path
Compare against a pre-existing snapshot, exiting with code 1 if they do not match.

Outputs a diff if the snapshots do not match.

By default the comparison is done with .gas-snapshot.

--snap path
Output file for the snapshot. Default: .gas-snapshot.

Test Options

-m regex
--match regex
Only run test functions matching the specified regex pattern.
Deprecated: See --match-test.

--match-test regex
Only run test functions matching the specified regex pattern.

--no-match-test regex
Only run test functions that do not match the specified regex pattern.

--match-contract regex
Only run tests in contracts matching the specified regex pattern.

--no-match-contract regex
Only run tests in contracts that do not match the specified regex pattern.

--match-path glob
Only run tests in source files matching the specified glob pattern.

--no-match-path glob
Only run tests in source files that do not match the specified glob pattern.

--debug regex
Run a test in the debugger.

The argument passed to this flag is the name of the test function you want to run, and it works the same as --match-test.

If more than one test matches your specified criteria, you must add additional filters until only one test is found (see --match-contract and --match-path).

The matching test will be opened in the debugger regardless of the outcome of the test.

If the matching test is a fuzz test, then it will open the debugger on the first failure case. If the fuzz test does not fail, it will open the debugger on the last fuzz case.

For more fine-grained control of which fuzz case is run, see forge debug.

--gas-report
Print a gas report.

--allow-failure
Exit with code 0 even if a test fails.

--fail-fast
Stop running tests after the first failure.

--etherscan-api-key key
Etherscan API key. If set, traces are decoded using Etherscan if --fork-url is also set.
Environment: ETHERSCAN_API_KEY

EVM Options

-f url
--rpc-url url
--fork-url url
Fetch state over a remote endpoint instead of starting from an empty state.

If you want to fetch state from a specific block number, see --fork-block-number.

--fork-block-number block
Fetch state from a specific block number over a remote endpoint. See --fork-url.

--fork-retry-backoff <BACKOFF>
Initial retry backoff on encountering errors.

--no-storage-caching
Explicitly disables the use of RPC caching.

All storage slots are read entirely from the endpoint. See --fork-url.

-v
--verbosity
Verbosity of the EVM.

Pass multiple times to increase the verbosity (e.g. -v, -vv, -vvv).

--sender address
The address which will be executing tests

--initial-balance balance
The initial balance of deployed contracts

--ffi
Enables the FFI cheatcode

Executor Options

--base-fee <FEE>
--block-base-fee-per-gas <FEE>
The base fee in a block (in wei).

--block-coinbase address
The coinbase of the block.

--block-difficulty difficulty
The block difficulty.

--block-gas-limit gas_limit
The block gas limit.

--block-number block
The block number.

--block-timestamp timestamp
The timestamp of the block (in seconds).

--chain-id chain_id
The chain ID.

--gas-limit gas_limit
The block gas limit.

--gas-price gas_price
The gas price (in wei).

--tx-origin address
The transaction origin.

Cache Options

--force
Clear the cache and artifacts folder and recompile.

Linker Options

--libraries libraries
Set pre-linked libraries.

The parameter must be in the format <remapped path to lib>:<library name>:<address>, e.g. src/Contract.sol:Library:0x....

Can also be set in your configuration file as libraries = ["<path>:<lib name>:<address>"].

Compiler Options

--optimize
Activate the Solidity optimizer.

--optimizer-runs runs
The number of optimizer runs.

--via-ir
Use the Yul intermediate representation compilation pipeline.

--revert-strings
How to treat revert and require reason strings.

--use solc_version
Specify the solc version, or a path to a local solc, to build with.

Valid values are in the format x.y.z, solc:x.y.z or path/to/solc.

--offline
Do not access the network. Missing solc versions will not be installed.

--no-auto-detect
Do not auto-detect solc.

--ignored-error-codes error_codes
Ignore solc warnings by error code. The parameter is a comma-separated list of error codes.

--extra-output selector
Extra output to include in the contract's artifact.

Example keys: abi, storageLayout, evm.assembly, ewasm, ir, ir-optimized, metadata.

For a full description, see the Solidity docs.

--extra-output-files selector
Extra output to write to separate files.

Example keys: abi, storageLayout, evm.assembly, ewasm, ir, ir-optimized, metadata.

For a full description, see the Solidity docs.

--evm-version version
The target EVM version.

Project Options

--build-info
Generate build info files.

--build-info-path path
Output path to directory that build info files will be written to.

--root path
The project's root path. By default, this is the root directory of the current git repository, or the current working directory.

-C path
--contracts path
The contracts source directory.
Environment: DAPP_SRC

--lib-paths path
The path to the library folder.

-R remappings
--remappings remappings
The project's remappings.

The parameter is a comma-separated list of remappings in the format <source>=<dest>.

--cache-path path
The path to the compiler cache.

--config-path file
Path to the config file.

--hh
--hardhat
This is a convenience flag, and is the same as passing --contracts contracts --lib-paths node-modules.

-o path
--out path
The project's artifacts directory.

--silent
Suppress all output.

Display Options

-j
--json
Print the deployment information as JSON.

Common Options

-h
--help
Prints help information.

EXAMPLES

Create a snapshot:
```
forge snapshot
```
Generate a diff:
```
forge snapshot --diff
```
Check that the snapshots match:
```
forge snapshot --check
```

forge coverage

NAME

forge-coverage - Displays which parts of your code are covered by tests.

SYNOPSIS

forge coverage [options]

DESCRIPTION

Displays which parts of your code are covered by tests.

Options

Report Options

--report allows you to specify the report type to use for coverage. This flag can be used multiple times.

It has three different options and is set to summary by default.

summary
Outputs a chart showing what percentage of your code is covered by tests.

lcov
Creates a lcov.info file containing your coverage data in the root of your project's directory.

debug
Outputs lines describing the location of uncovered code.

Common Options

-h
--help
Prints help information.

EXAMPLES

View summarized coverage:
```
forge coverage
```
Create lcov file with coverage data:
```
forge coverage --report lcov
```
Output uncovered code locations:
```
forge coverage --report debug
```

Deploy Commands

forge create

NAME

forge-create - Deploy a smart contract.

SYNOPSIS

forge create [options] contract

DESCRIPTION

Deploy a smart contract.

The path to the contract is in the format <path>:<contract>, e.g. src/Contract.sol:Contract.

You can specify constructor arguments with --constructor-args. Alternatively, you can specify a file containing space-separated constructor arguments with --constructor-args-path.

Dynamic linking is not supported: you should predeploy your libraries and manually specify their addresses (see --libraries).

ℹ️ Note

The --constructor-args flag must be positioned last in the command, since it takes multiple values.

OPTIONS

Build Options

--constructor-args args...
The constructor arguments.

--constructor-args-path file
The path to a file containing the constructor arguments.

--verify
Verify contract after creation. Runs forge verify-contract with the appropriate parameters.

--verifier name
The verification provider. Available options: etherscan, sourcify & blockscout. Default: etherscan.

--verifier-url url
The optional verifier url for submitting the verification request.
Environment: VERIFIER_URL

--unlocked
Send via eth_sendTransaction using the --from argument or $ETH_FROM as sender.

Transaction Options

--gas-limit gas_limit
Gas limit for the transaction.

--gas-price price
Gas price for the transaction, or max fee per gas for EIP1559 transactions.

--priority-gas-price price
Max priority fee per gas for EIP1559 transactions.

--value value
Ether to send in the transaction.

    Either specified as an integer (wei), or as a string with a unit, for example:
    - 1ether
    - 10gwei
    - 0.01ether

--nonce nonce
Nonce for the transaction.

--legacy
Send a legacy transaction instead of an EIP1559 transaction.

This is automatically enabled for common networks without EIP1559.

WALLET OPTIONS - RAW:

-i
--interactive <NUM>
Open an interactive prompt to enter your private key. Takes a value for the number of keys to enter.
Defaults to 0.

--mnemonic-derivation-path <PATHS>
The wallet derivation path. Works with both --mnemonic-path and hardware wallets.

--mnemonic-indexes <INDEXES>
Use the private key from the given mnemonic index. Used with --mnemonic-paths.
Defaults to 0.

--mnemonic-passphrase <PASSPHRASE>
Use a BIP39 passphrases for the mnemonic.

--mnemonic <PATHS>
Use the mnemonic phrases or mnemonic files at the specified paths.

--private-key <RAW_PRIVATE_KEY>
Use the provided private key.

--private-keys <RAW_PRIVATE_KEYS>
Use the provided private keys.

Wallet Options - Keystore

--keystore path
Use the keystore in the given folder or file.
Environment: ETH_KEYSTORE

--password password
The keystore password. Used with --keystore.

Wallet Options - Hardware Wallet

-t
--trezor
Use a Trezor hardware wallet.

-l
--ledger
Use a Ledger hardware wallet.

Wallet Options - Remote

-f address
--from address
Sign the transaction with the specified account on the RPC.
Environment: ETH_FROM

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

--flashbots
Use the Flashbots RPC URL (https://rpc.flashbots.net).

Etherscan Options

--chain chain_name
The Etherscan chain.

--etherscan-api-key key
Etherscan API key, or the key of an Etherscan configuration table.
Environment: ETHERSCAN_API_KEY

Cache Options

--force
Clear the cache and artifacts folder and recompile.

Linker Options

--libraries libraries
Set pre-linked libraries.

The parameter must be in the format <remapped path to lib>:<library name>:<address>, e.g. src/Contract.sol:Library:0x....

Can also be set in your configuration file as libraries = ["<path>:<lib name>:<address>"].

Compiler Options

--optimize
Activate the Solidity optimizer.

--optimizer-runs runs
The number of optimizer runs.

--via-ir
Use the Yul intermediate representation compilation pipeline.

--revert-strings
How to treat revert and require reason strings.

--use solc_version
Specify the solc version, or a path to a local solc, to build with.

Valid values are in the format x.y.z, solc:x.y.z or path/to/solc.

--offline
Do not access the network. Missing solc versions will not be installed.

--no-auto-detect
Do not auto-detect solc.

--ignored-error-codes error_codes
Ignore solc warnings by error code. The parameter is a comma-separated list of error codes.

--extra-output selector
Extra output to include in the contract's artifact.

Example keys: abi, storageLayout, evm.assembly, ewasm, ir, ir-optimized, metadata.

For a full description, see the Solidity docs.

--extra-output-files selector
Extra output to write to separate files.

Example keys: abi, storageLayout, evm.assembly, ewasm, ir, ir-optimized, metadata.

For a full description, see the Solidity docs.

--evm-version version
The target EVM version.

Project Options

--build-info
Generate build info files.

--build-info-path path
Output path to directory that build info files will be written to.

--root path
The project's root path. By default, this is the root directory of the current git repository, or the current working directory.

-C path
--contracts path
The contracts source directory.
Environment: DAPP_SRC

--lib-paths path
The path to the library folder.

-R remappings
--remappings remappings
The project's remappings.

The parameter is a comma-separated list of remappings in the format <source>=<dest>.

--cache-path path
The path to the compiler cache.

--config-path file
Path to the config file.

--hh
--hardhat
This is a convenience flag, and is the same as passing --contracts contracts --lib-paths node-modules.

-o path
--out path
The project's artifacts directory.

--silent
Suppress all output.

Display Options

-j
--json
Print the deployment information as JSON.

Common Options

-h
--help
Prints help information.

EXAMPLES

Deploy a contract with no constructor arguments:

forge create src/Contract.sol:ContractWithNoConstructor

Deploy a contract with two constructor arguments:

forge create src/Contract.sol:MyToken --constructor-args "My Token" "MT"

forge verify-contract

NAME

forge-verify-contract - Verify smart contracts on a chosen verification provider.

SYNOPSIS

forge verify-contract [options] address contract

DESCRIPTION

Verifies a smart contract on a chosen verification provider.

You must provide:

The contract address
The contract name or the path to the contract (read below) In case of Etherscan verification, you must also provide:
Your Etherscan API key, either by passing it as an argument or setting ETHERSCAN_API_KEY

To find the exact compiler version, run ~/.svm/x.y.z/solc-x.y.z --version and search for the 8 hex digits in the version string here.

The path to the contract is in the format <path>:<contract>, e.g. src/Contract.sol:Contract.

By default, smart contracts are verified in a multi-file fashion. If you want to flatten the contract before verifying, pass --flatten.

This command will try to compile the source code of the flattened contract if --flatten is passed before verifying. If you do not want that, pass --force.

You can specify ABI-encoded constructor arguments with --constructor-args. Alternatively, you can specify a file containing space-separated constructor arguments with --constructor-args-path. (Note that cache must be enabled in the config for the latter to work.)

OPTIONS

Verify Contract Options

--verifier name
The verification provider. Available options: etherscan, sourcify & blockscout. Default: etherscan.

--verifier-url url
The optional verifier url for submitting the verification request.
Environment: VERIFIER_URL

--compiler-version version
The compiler version used to build the smart contract.

To find the exact compiler version, run ~/.svm/x.y.z/solc-x.y.z --version where x and y are major and minor version numbers respectively, then search for the 8 hex digits in the version string here.

--num-of-optimizations num
--optimizer-runs num
The number of optimization runs used to build the smart contract.

--constructor-args args
The ABI-encoded constructor arguments. Conflicts with --constructor-args-path.

--constructor-args-path file
The path to a file containing the constructor arguments. Conflicts with --constructor-args.

--chain-id chain
--chain chain
The ID or name of the chain the contract is deployed to.
Default: mainnet

--flatten
Flag indicating whether to flatten the source code before verifying.

If this flag is not provided, the JSON standard input will be used instead.

-f
--force
Do not compile the flattened smart contract before verifying.

--delay delay
Optional timeout to apply in between attempts in seconds. Defaults to 3.

--retries retries
Number of attempts for retrying. Defaults to 15.

--watch
Wait for verification result after submission.
Automatically runs forge verify-check until the verification either fails or succeeds.

Project Options

--build-info
Generate build info files.

--build-info-path path
Output path to directory that build info files will be written to.

--root path
The project's root path. By default, this is the root directory of the current git repository, or the current working directory.

-C path
--contracts path
The contracts source directory.
Environment: DAPP_SRC

--lib-paths path
The path to the library folder.

-R remappings
--remappings remappings
The project's remappings.

The parameter is a comma-separated list of remappings in the format <source>=<dest>.

--cache-path path
The path to the compiler cache.

--config-path file
Path to the config file.

--hh
--hardhat
This is a convenience flag, and is the same as passing --contracts contracts --lib-paths node-modules.

Common Options

-h
--help
Prints help information.

EXAMPLES

Verify a contract with JSON standard input on Etherscan

forge verify-contract <address> SomeContract --watch

Verify a contract on a custom Sourcify instance

forge verify-contract --verifier sourcify \
  --verifier-url http://localhost:5000 <address> SomeContract

Verify a flattened contract built with solc v0.8.11+commit.d7f03943:

forge verify-contract --flatten --watch --compiler-version "v0.8.11+commit.d7f03943" \
  --constructor-args $(cast abi-encode "constructor(string,string,uint256,uint256)" "ForgeUSD" "FUSD" 18 1000000000000000000000) \
  <address> MyToken

Verify a flattened contract by specifying constructor arguments in a file:

forge verify-contract --flatten --watch --compiler-version "v0.8.11+commit.d7f03943" \
  --constructor-args-path constructor-args.txt <address> src/Token.sol:MyToken

where constructor-args.txt contains the following content:

ForgeUSD FUSD 18 1000000000000000000000

forge verify-check

NAME

forge-verify-check - Check verification status on a chosen verification provider.

SYNOPSIS

forge verify-check [options] id [etherscan_key]

The id is the verification identifier. For Etherscan & Bloxroute - it is the submission GUID, for Sourcify - it's the contract address.

DESCRIPTION

Check verification status on a chosen verification provider.

For Etherscan, you must provide an Etherscan API key, either by passing it as an argument or setting ETHERSCAN_API_KEY

OPTIONS

Verify Contract Options

--verifier name
The verification provider. Available options: etherscan, sourcify & blockscout. Default: etherscan.

--verifier-url url
The optional verifier url for submitting the verification request.
Environment: VERIFIER_URL

--chain-id chain_id
The chain ID the contract is deployed to (either a number or a chain name).
Default: mainnet

--delay delay
Optional timeout to apply in between attempts in seconds. Defaults to 3.

--retries retries
Number of attempts for retrying. Defaults to 15.

Common Options

-h
--help
Prints help information.

forge flatten

NAME

forge-flatten - Flatten a source file and all of its imports into one file.

SYNOPSIS

forge flatten [options] file

DESCRIPTION

Flatten a source file and all of its imports into one file.

If --output <FILE> is not set, then the flattened contract will be output to stdout.

OPTIONS

Flatten Options

-o file
--output file
The path to output the flattened contract. If not specified, the flattened contract will be output to stdout.

Project Options

--build-info
Generate build info files.

--build-info-path path
Output path to directory that build info files will be written to.

--root path
The project's root path. By default, this is the root directory of the current git repository, or the current working directory.

-C path
--contracts path
The contracts source directory.
Environment: DAPP_SRC

--lib-paths path
The path to the library folder.

-R remappings
--remappings remappings
The project's remappings.

The parameter is a comma-separated list of remappings in the format <source>=<dest>.

--cache-path path
The path to the compiler cache.

--config-path file
Path to the config file.

--hh
--hardhat
This is a convenience flag, and is the same as passing --contracts contracts --lib-paths node-modules.

Common Options

-h
--help
Prints help information.

EXAMPLES

Flatten src/Contract.sol:
```
forge flatten src/Contract.sol
```
Flatten src/Contract.sol and write the result to src/Contract.flattened.sol:
```
forge flatten --output src/Contract.flattened.sol src/Contract.sol
```

Utility Commands

forge debug

NAME

forge-debug - Debug a single smart contract as a script.

SYNOPSIS

forge debug [options] path [args...]

DESCRIPTION

Debugs a single smart contract located in the source file (path) as a script.

If multiple contracts are in the specified source file, you must pass --target-contract to specify what contract you want to run.

Calls

After the script is deployed to the internal EVM a call is made to a function with the signature setUp(), if present.

By default, the script is assumed to be contained in a function with the signature run(). If you wish to run a different function, pass --sig <SIGNATURE>.

The signature can be a fragment (<function name>(<types>)), or raw calldata.

If you pass a fragment, and the function has parameters, you can add the call parameters to the end of the command (args).

Forking

It is possible to run the script in a forked environment by passing --fork-url <URL>.

When the script is running in a forked environment, you can access all the state of the forked chain as you would if you had deployed the script. Cheatcodes are still available.

Debugging

It is possible to run the script in an interactive debugger. To start the debugger, pass --debug.

More information on the debugger can be found in the debugger chapter.

OPTIONS

Debug Options

--target-contract contract_name
The name of the contract you want to run

-s signature
--sig signature
The signature of the function you want to call in the contract, or raw calldata. Default: run()

--debug
Open the script in the debugger.

EVM Options

-f url
--rpc-url url
--fork-url url
Fetch state over a remote endpoint instead of starting from an empty state.

If you want to fetch state from a specific block number, see --fork-block-number.

--fork-block-number block
Fetch state from a specific block number over a remote endpoint. See --fork-url.

--fork-retry-backoff <BACKOFF>
Initial retry backoff on encountering errors.

--no-storage-caching
Explicitly disables the use of RPC caching.

All storage slots are read entirely from the endpoint. See --fork-url.

-v
--verbosity
Verbosity of the EVM.

Pass multiple times to increase the verbosity (e.g. -v, -vv, -vvv).

--sender address
The address which will be executing tests

--initial-balance balance
The initial balance of deployed contracts

--ffi
Enables the FFI cheatcode

Executor Options

--base-fee <FEE>
--block-base-fee-per-gas <FEE>
The base fee in a block (in wei).

--block-coinbase address
The coinbase of the block.

--block-difficulty difficulty
The block difficulty.

--block-gas-limit gas_limit
The block gas limit.

--block-number block
The block number.

--block-timestamp timestamp
The timestamp of the block (in seconds).

--chain-id chain_id
The chain ID.

--gas-limit gas_limit
The block gas limit.

--gas-price gas_price
The gas price (in wei).

--tx-origin address
The transaction origin.

Cache Options

--force
Clear the cache and artifacts folder and recompile.

Linker Options

--libraries libraries
Set pre-linked libraries.

The parameter must be in the format <remapped path to lib>:<library name>:<address>, e.g. src/Contract.sol:Library:0x....

Can also be set in your configuration file as libraries = ["<path>:<lib name>:<address>"].

Compiler Options

--optimize
Activate the Solidity optimizer.

--optimizer-runs runs
The number of optimizer runs.

--via-ir
Use the Yul intermediate representation compilation pipeline.

--revert-strings
How to treat revert and require reason strings.

--use solc_version
Specify the solc version, or a path to a local solc, to build with.

Valid values are in the format x.y.z, solc:x.y.z or path/to/solc.

--offline
Do not access the network. Missing solc versions will not be installed.

--no-auto-detect
Do not auto-detect solc.

--ignored-error-codes error_codes
Ignore solc warnings by error code. The parameter is a comma-separated list of error codes.

--extra-output selector
Extra output to include in the contract's artifact.

Example keys: abi, storageLayout, evm.assembly, ewasm, ir, ir-optimized, metadata.

For a full description, see the Solidity docs.

--extra-output-files selector
Extra output to write to separate files.

Example keys: abi, storageLayout, evm.assembly, ewasm, ir, ir-optimized, metadata.

For a full description, see the Solidity docs.

--evm-version version
The target EVM version.

Project Options

--build-info
Generate build info files.

--build-info-path path
Output path to directory that build info files will be written to.

--root path
The project's root path. By default, this is the root directory of the current git repository, or the current working directory.

-C path
--contracts path
The contracts source directory.
Environment: DAPP_SRC

--lib-paths path
The path to the library folder.

-R remappings
--remappings remappings
The project's remappings.

The parameter is a comma-separated list of remappings in the format <source>=<dest>.

--cache-path path
The path to the compiler cache.

--config-path file
Path to the config file.

--hh
--hardhat
This is a convenience flag, and is the same as passing --contracts contracts --lib-paths node-modules.

-o path
--out path
The project's artifacts directory.

--silent
Suppress all output.

Common Options

-h
--help
Prints help information.

EXAMPLES

Execute the run() function in a contract:
```
forge debug src/Contract.sol
```
Open a script in the debugger:
```
forge debug src/Contract.sol --debug
```

Execute the foo() function in a contract:

forge debug src/Contract.sol --sig "foo()"

Execute a contract with a function that takes parameters:

forge debug src/Contract.sol --sig "foo(string,uint256)" "hello" 100

Execute a contract with raw calldata:

forge debug src/Contract.sol --sig "0x..."

forge bind

NAME

forge-bind - Generate Rust bindings for smart contracts.

SYNOPSIS

forge bind [options]

DESCRIPTION

Generates Rust bindings for smart contracts using ethers-rs.

The bindings are generated from the project's artifacts, which by default is ./out/. If you want to generate bindings for artifacts in a different directory, pass --bindings-path <PATH>.

There are three output options:

Generate bindings in a crate (default)
Generate bindings in a module by passing --module
Generate bindings in a single file by passing --single-file

By default, the command will check that existing bindings are correct and exit accordingly. You can overwrite the existing bindings by passing --overwrite.

OPTIONS

Project Options

-b path
--bindings-path path
The project's root path. By default, this is the root directory of the current git repository, or the current working directory.

--crate-name name
The name of the Rust crate to generate, if you are generating a crate (default).
This should be a valid crates.io crate name.

Default: foundry-contracts

--crate-version semver
The version of the Rust crate to generate, if you are generating a crate (default).
This should be a standard semver version string.

Default: 0.0.1

--module
Generate the bindings as a module instead of a crate.

--single-file
Generate bindings as a single file.

--overwrite
Overwrite existing generated bindings. By default, the command will check that the bindings are correct, and then exit.
If --overwrite is passed, it will instead delete and overwrite the bindings.

--root path
The project's root path. By default, this is the root directory of the current git repository, or the current working directory.

--skip-cargo-toml
    Skip Cargo.toml consistency checks.
    This allows you to manage the ethers version without giving up on consistency checks.
    An example would be if you use additional features of ethers like ws, ipc, or rustls and get an ethers-providers version mismatch.

--skip-build
Skips running forge build before generating binding.
This allows you to skip the default forge build step that's executed first and instead generate bindings using the already existing artifacts.

--select-all
By default all contracts ending with Test or Script are excluded. This will explicitly generate bindings for all contracts. Conflicts with --select and --skip.

--select regex+
Create bindings only for contracts whose names match the specified filter(s). Conflicts with --skip.

--skip regex+
Create bindings only for contracts whose names do not match the specified filter(s). Conflicts with --select.

Common Options

-h
--help
Prints help information.

Cache Options

--force
Clear the cache and artifacts folder and recompile.

Linker Options

--libraries libraries
Set pre-linked libraries.

The parameter must be in the format <remapped path to lib>:<library name>:<address>, e.g. src/Contract.sol:Library:0x....

Can also be set in your configuration file as libraries = ["<path>:<lib name>:<address>"].

Compiler Options

--optimize
Activate the Solidity optimizer.

--optimizer-runs runs
The number of optimizer runs.

--via-ir
Use the Yul intermediate representation compilation pipeline.

--revert-strings
How to treat revert and require reason strings.

--use solc_version
Specify the solc version, or a path to a local solc, to build with.

Valid values are in the format x.y.z, solc:x.y.z or path/to/solc.

--offline
Do not access the network. Missing solc versions will not be installed.

--no-auto-detect
Do not auto-detect solc.

--ignored-error-codes error_codes
Ignore solc warnings by error code. The parameter is a comma-separated list of error codes.

--extra-output selector
Extra output to include in the contract's artifact.

Example keys: abi, storageLayout, evm.assembly, ewasm, ir, ir-optimized, metadata.

For a full description, see the Solidity docs.

--extra-output-files selector
Extra output to write to separate files.

Example keys: abi, storageLayout, evm.assembly, ewasm, ir, ir-optimized, metadata.

For a full description, see the Solidity docs.

--evm-version version
The target EVM version.

Project Options

--build-info
Generate build info files.

--build-info-path path
Output path to directory that build info files will be written to.

--root path
The project's root path. By default, this is the root directory of the current git repository, or the current working directory.

-C path
--contracts path
The contracts source directory.
Environment: DAPP_SRC

--lib-paths path
The path to the library folder.

-R remappings
--remappings remappings
The project's remappings.

The parameter is a comma-separated list of remappings in the format <source>=<dest>.

--cache-path path
The path to the compiler cache.

--config-path file
Path to the config file.

--hh
--hardhat
This is a convenience flag, and is the same as passing --contracts contracts --lib-paths node-modules.

-o path
--out path
The project's artifacts directory.

--silent
Suppress all output.

`forge cache`

NAME

forge-cache - Manage the Foundry cache.

SYNOPSIS

forge cache [options] command [args]
forge cache [options] --version
forge cache [options] --help

DESCRIPTION

This program is a set of tools to manage the Foundry cache.

COMMANDS

forge cache clean
Cleans cached data from ~/.foundry.

forge cache ls
Shows cached data from ~/.foundry.

OPTIONS

Special Options

-V
--version
Print version info and exit.

Common Options

-h
--help
Prints help information.

`forge cache clean`

NAME

forge-cache-clean - Cleans cached data from ~/.foundry.

SYNOPSIS

forge cache clean [options] [--] [chains..]

DESCRIPTION

Removes files in the ~/.foundry/cache folder which is used to cache Etherscan verification status and block data.

OPTIONS

-b
--blocks
One or more block numbers separated by comma with no spaces

--etherscan A boolean flag that specifies to only remove the block explorer portion of the cache

Common Options

-h
--help
Prints help information.

EXAMPLES

Remove the entire cache (also, forge cache clean is an alias for this)
```
forge cache clean all
```
Remove the entire block explorer cache
```
forge cache clean all --etherscan
```
Remove cache data for a specific chain, by name
```
forge cache clean rinkeby
```
Remove cache data for a specific block number on a specific chain. Does not work if chain is all
```
forge cache clean rinkeby -b 150000
```
Remove block explorer cache data for a specific chain. Does not work if --blocks are specified.
```
forge cache clean rinkeby --etherscan
```
Specify multiple chains
```
forge cache clean rinkeby mainnet
```

Specify multiple blocks

forge cache clean rinkeby --blocks 530000,9000000,9200000

`forge cache ls`

NAME

forge-cache-ls - Shows cached data from ~/.foundry.

SYNOPSIS

forge cache ls [chains..]

DESCRIPTION

Lists what is in the ~/.foundry/cache folder currently.

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Show the entire cache (also, forge cache ls is an alias for this)
```
forge cache ls all
```
Show cache data for a specific chain, by name
```
forge cache ls rinkeby
```
Specify multiple chains
```
forge cache ls rinkeby mainnet
```

forge script

NAME

forge-script - Run a smart contract as a script, building transactions that can be sent onchain.

SYNOPSIS

forge script [options] path [args...]

DESCRIPTION

Run a smart contract as a script, building transactions that can be sent onchain.

Scripts can be used to apply state transitions on live contracts, or deploy and initialize a complex set of smart contracts using Solidity.

OPTIONS

--broadcast
Broadcasts the transactions.

--debug
Open the script in the debugger. Takes precedence over broadcast.

-g
--gas-estimate-multiplier multiplier
Relative percentage by which to multiply all gas estimates. (i.e. set to 200 to double them) Default: 130

--json
Output results in JSON format.
Note: The output is under development and prone to change.

--legacy
Use legacy transactions instead of EIP1559 ones. This is auto-enabled for common networks without EIP1559.

--resume
Resumes submitting transactions that failed or timed-out previously.

-s
--sig signature
The signature of the function you want to call in the contract, or raw calldata.
Default: run()

--skip-simulation
Skips on-chain simulation.

--slow
Makes sure a transaction is sent, only after its previous one has been confirmed and succeeded.

--target-contract contract_name
The name of the contract you want to run.

--with-gas-price price
Sets the gas price for broadcasted legacy transactions, or the max fee for broadcasted EIP1559 transactions.
Note: To set the gas price in the execution environment of the script use --gas-price instead (see below).

Etherscan Options

--chain chain_name
The Etherscan chain.

--etherscan-api-key key
Etherscan API key, or the key of an Etherscan configuration table.
Environment: ETHERSCAN_API_KEY

Verification Options

--verify
If it finds a matching broadcast log, it tries to verify every contract found in the receipts.

--verifier name
The verification provider. Available options: etherscan, sourcify & blockscout. Default: etherscan.

--verifier-url url
The optional verifier url for submitting the verification request.
Environment: VERIFIER_URL

--delay delay
Optional timeout to apply in between attempts in seconds. Defaults to 3.

--retries retries
Number of attempts for retrying. Defaults to 15.

Cache Options

--force
Clear the cache and artifacts folder and recompile.

Linker Options

--libraries libraries
Set pre-linked libraries.

The parameter must be in the format <remapped path to lib>:<library name>:<address>, e.g. src/Contract.sol:Library:0x....

Can also be set in your configuration file as libraries = ["<path>:<lib name>:<address>"].

Compiler Options

--optimize
Activate the Solidity optimizer.

--optimizer-runs runs
The number of optimizer runs.

--via-ir
Use the Yul intermediate representation compilation pipeline.

--revert-strings
How to treat revert and require reason strings.

--use solc_version
Specify the solc version, or a path to a local solc, to build with.

Valid values are in the format x.y.z, solc:x.y.z or path/to/solc.

--offline
Do not access the network. Missing solc versions will not be installed.

--no-auto-detect
Do not auto-detect solc.

--ignored-error-codes error_codes
Ignore solc warnings by error code. The parameter is a comma-separated list of error codes.

--extra-output selector
Extra output to include in the contract's artifact.

Example keys: abi, storageLayout, evm.assembly, ewasm, ir, ir-optimized, metadata.

For a full description, see the Solidity docs.

--extra-output-files selector
Extra output to write to separate files.

Example keys: abi, storageLayout, evm.assembly, ewasm, ir, ir-optimized, metadata.

For a full description, see the Solidity docs.

--evm-version version
The target EVM version.

Project Options

--build-info
Generate build info files.

--build-info-path path
Output path to directory that build info files will be written to.

--root path
The project's root path. By default, this is the root directory of the current git repository, or the current working directory.

-C path
--contracts path
The contracts source directory.
Environment: DAPP_SRC

--lib-paths path
The path to the library folder.

-R remappings
--remappings remappings
The project's remappings.

The parameter is a comma-separated list of remappings in the format <source>=<dest>.

--cache-path path
The path to the compiler cache.

--config-path file
Path to the config file.

--hh
--hardhat
This is a convenience flag, and is the same as passing --contracts contracts --lib-paths node-modules.

-o path
--out path
The project's artifacts directory.

--silent
Suppress all output.

Build Options

--names
Print compiled contract names.

--sizes
Print compiled non-test contract sizes, exiting with code 1 if any of them are above the size limit.

Watch Options

-w [path...]
--watch [path...]
Watch specific file(s) or folder(s).

By default, the project's source directory is watched.

-d delay
--delay delay
File update debounce delay.

Defaults to 50ms. Parses as decimal seconds by default, but using an integer with the ms suffix may be more convenient.

When using --poll mode, you'll want a larger duration, or risk overloading disk I/O.

--no-restart
Do not restart the command while it's running.

--run-all
Explicitly re-run the command on all files when a change is made.

Wallet Options - Raw

-i --interactives num
Open an interactive prompt to enter your private key. Takes a value for the number of keys to enter.
Default: 0

--mnemonic-indexes indexes
Use the private key from the given mnemonic index. Used with --mnemonic-path.
Default: 0

--mnemonic-paths paths
Use the mnemonic file at the specified path(s).

--private-key raw_private_key
Use the provided private key.

--private-keys raw_private_keys
Use the provided private keys.

Wallet Options - Keystore

--keystores paths
Use the keystores in the given folders or files.
Environment: ETH_KEYSTORE

--password passwords
The keystore passwords. Used with --keystore.

Wallet Options - Hardware Wallet

-t
--trezor
Use a Trezor hardware wallet.

-l
--ledger
Use a Ledger hardware wallet.

--hd-paths paths
The derivation paths to use with hardware wallets.

Wallet Options - Remote

-a addresses
--froms addresses
Sign the transaction with the specified accounts on the RPC.
Environment: ETH_FROM

EVM Options

-f url
--rpc-url url
--fork-url url
Fetch state over a remote endpoint instead of starting from an empty state.

If you want to fetch state from a specific block number, see --fork-block-number.

--fork-block-number block
Fetch state from a specific block number over a remote endpoint. See --fork-url.

--fork-retry-backoff <BACKOFF>
Initial retry backoff on encountering errors.

--no-storage-caching
Explicitly disables the use of RPC caching.

All storage slots are read entirely from the endpoint. See --fork-url.

-v
--verbosity
Verbosity of the EVM.

Pass multiple times to increase the verbosity (e.g. -v, -vv, -vvv).

--sender address
The address which will be executing tests

--initial-balance balance
The initial balance of deployed contracts

--ffi
Enables the FFI cheatcode

Executor Options

--base-fee <FEE>
--block-base-fee-per-gas <FEE>
The base fee in a block (in wei).

--block-coinbase address
The coinbase of the block.

--block-difficulty difficulty
The block difficulty.

--block-gas-limit gas_limit
The block gas limit.

--block-number block
The block number.

--block-timestamp timestamp
The timestamp of the block (in seconds).

--chain-id chain_id
The chain ID.

--gas-limit gas_limit
The block gas limit.

--gas-price gas_price
The gas price (in wei).

--tx-origin address
The transaction origin.

Common Options

-h
--help
Prints help information.

EXAMPLES

Run BroadcastTest as a script, broadcasting generated transactions on-chain

forge script ./test/Broadcast.t.sol --tc BroadcastTest --sig "deploy()" \
    -vvv --fork-url $GOERLI_RPC_URL

Deploy a contract on Polygon (see scripting tutorial for an example script). The verifier url is different for every network.

forge script script/NFT.s.sol:MyScript --chain-id 137 --rpc-url $RPC_URL \
    --etherscan-api-key $POLYGONSCAN_API_KEY --verifier-url https://api.polygonscan.com/api \
    --broadcast --verify -vvvv

Resume a failed script. Using the above as an example, remove --broadcast add --resume

forge script script/NFT.s.sol:MyScript --chain-id 137 --rpc-url $RPC_URL \
    --etherscan-api-key $POLYGONSCAN_API_KEY --verifier-url https://api.polygonscan.com/api \
    --verify -vvvv --resume

Verify contracts that were just deployed with a script

forge script script/NFT.s.sol --rpc-url $RPC_URL --verify --resume

forge upload-selectors

NAME

forge-upload-selectors - Uploads abi of given contract to https://sig.eth.samczsun.com function selector database.

SYNOPSIS

forge upload-selectors [options] contract

DESCRIPTION

Uploads abi of given contract to https://sig.eth.samczsun.com function selector database.

OPTIONS

Project Options

--build-info
Generate build info files.

--build-info-path path
Output path to directory that build info files will be written to.

--root path
The project's root path. By default, this is the root directory of the current git repository, or the current working directory.

-C path
--contracts path
The contracts source directory.
Environment: DAPP_SRC

--lib-paths path
The path to the library folder.

-R remappings
--remappings remappings
The project's remappings.

The parameter is a comma-separated list of remappings in the format <source>=<dest>.

--cache-path path
The path to the compiler cache.

--config-path file
Path to the config file.

--hh
--hardhat
This is a convenience flag, and is the same as passing --contracts contracts --lib-paths node-modules.

Common Options

-h
--help
Prints help information.

EXAMPLES

Upload ABI to selector database

forge upload-selectors LinearVestingVault

forge doc

NAME

forge-doc - Generate documentation for Solidity source files.

SYNOPSIS

forge doc [options]

DESCRIPTION

Generates and builds an mdbook from Solidity source files.

OPTIONS

--root path
The project's root path. By default, this is the root directory of the current git repository, or the current working directory.

--out path The output path for the generated mdbook. By default, it is the docs/ in project root.

--build Build the mdbook from generated files.

--serve Serve the documentation locally.

--hostname hostname Hostname for serving documentation. Requires --serve.

--port port Port for serving documentation. Requires --serve.

Common Options

-h
--help
Prints help information.

EXAMPLES

Generate documentation.
```
forge doc
```
Generate and build documentation with specified output directory.
```
forge doc --build --out ./documentation
```
Generate and serve documentation locally on port 4000.
```
forge doc --serve --port 4000
```

cast Commands

General Commands

cast

NAME

cast - Perform Ethereum RPC calls from the comfort of your command line.

SYNOPSIS

cast [options] command [args] cast [options] --version cast [options] --help

DESCRIPTION

This program is a set of tools to interact with Ethereum and perform conversions.

COMMANDS

General Commands

cast help Display help information about Cast.

cast completions Generate shell autocompletions for Cast.

Chain Commands

cast chain-id Get the Ethereum chain ID.

cast chain Get the symbolic name of the current chain.

cast client Get the current client version.

Transaction Commands

cast publish Publish a raw transaction to the network.

cast receipt Get the transaction receipt for a transaction.

cast send Sign and publish a transaction.

cast call Perform a call on an account without publishing a transaction.

cast rpc Perform a raw JSON-RPC request [aliases: rp]

cast tx Get information about a transaction.

cast run Runs a published transaction in a local environment and prints the trace.

cast estimate Estimate the gas cost of a transaction.

cast access-list Create an access list for a transaction.

Block Commands

cast find-block Get the block number closest to the provided timestamp.

cast gas-price Get the current gas price.

cast block-number Get the latest block number.

cast basefee Get the basefee of a block.

cast block Get information about a block.

cast age Get the timestamp of a block.

Account Commands

cast balance Get the balance of an account in wei.

cast storage Get the raw value of a contract's storage slot.

cast proof Generate a storage proof for a given storage slot.

cast nonce Get the nonce for an account.

cast code Get the bytecode of a contract.

cast codesize Get the runtime bytecode size of a contract.

ENS Commands

cast lookup-address Perform an ENS reverse lookup.

cast resolve-name Perform an ENS lookup.

cast namehash Calculate the ENS namehash of a name.

Etherscan Commands

cast etherscan-source Get the source code of a contract from Etherscan.

ABI Commands

cast abi-encode ABI encode the given function arguments, excluding the selector.

cast 4byte Get the function signatures for the given selector from https://sig.eth.samczsun.com.

cast 4byte-decode Decode ABI-encoded calldata using https://sig.eth.samczsun.com.

cast 4byte-event Get the event signature for a given topic 0 from https://sig.eth.samczsun.com.

cast calldata ABI-encode a function with arguments.

cast pretty-calldata Pretty print calldata.

cast --abi-decode Decode ABI-encoded input or output data.

cast --calldata-decode Decode ABI-encoded input data.

cast upload-signature Upload the given signatures to https://sig.eth.samczsun.com.

Conversion Commands

cast --format-bytes32-string Formats a string into bytes32 encoding.

cast --from-bin Convert binary data into hex data.

cast --from-fix Convert a fixed point number into an integer.

cast --from-utf8 Convert UTF8 to hex.

cast --parse-bytes32-string Parses a string from bytes32 encoding.

cast --to-ascii Convert hex data to an ASCII string.

cast --to-base Convert a number of one base to another.

cast --to-bytes32 Right-pads hex data to 32 bytes.

cast --to-fix Convert an integer into a fixed point number.

cast --to-hexdata Normalize the input to lowercase, 0x-prefixed hex.

cast --to-int256 Convert a number to a hex-encoded int256.

cast --to-uint256 Convert a number to a hex-encoded uint256.

cast --to-unit Convert an ETH amount into another unit (ether, gwei, wei).

cast --to-wei Convert an ETH amount to wei.

cast shl Perform a left shifting operation.

cast shr Perform a right shifting operation.

Utility Commands

cast sig Get the selector for a function.

cast sig-event Generate event signatures from event string.

cast keccak Hash arbitrary data using keccak-256.

cast compute-address Compute the contract address from a given nonce and deployer address.

cast create2 Generate a deterministic contract address using CREATE2

cast interface Generate a Solidity interface from a given ABI.

cast index Compute the storage slot for an entry in a mapping.

cast --concat-hex Concatenate hex strings.

cast --max-int Get the maximum i256 value.

cast --min-int Get the minimum i256 value.

cast --max-uint Get the maximum u256 value.

cast --to-checksum-address Convert an address to a checksummed format (EIP-55).

Wallet Commands

cast wallet Wallet management utilities.

cast wallet new Create a new random keypair.

cast wallet address Convert a private key to an address.

cast wallet sign Sign a message.

cast wallet vanity Generate a vanity address.

cast wallet verify Verify the signature of a message.

OPTIONS

Special Options

-V --version Print version info and exit.

Common Options

-h
--help
Prints help information.

EXAMPLES

Call a function on a contract:

cast call 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2 \
  "balanceOf(address)(uint256)" 0x...

Decode raw calldata:

cast --calldata-decode "transfer(address,uint256)" \
  0xa9059cbb000000000000000000000000e78388b4ce79068e89bf8aa7f218ef6b9ab0e9d0000000000000000000000000000000000000000000000000008a8e4b1a3d8000

Encode calldata:

cast calldata "someFunc(address,uint256)" 0x... 1

BUGS

See https://github.com/foundry-rs/foundry/issues for issues.

cast help

NAME

cast-help - Get help for a Cast command

SYNOPSIS

cast help [subcommand]

DESCRIPTION

Prints a help message for the given command.

EXAMPLES

Get help for a command:
```
cast help call
```
Help is also available with the --help flag:
```
cast call --help
```

cast completions

NAME

cast-completions - Generate shell completions script

SYNOPSIS

cast completions shell

DESCRIPTION

Generates a shell completions script for the given shell.

Supported shells are:

bash
elvish
fish
powershell
zsh

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Generate shell completions script for zsh:

cast completions zsh > $HOME/.oh-my-zsh/completions/_cast

Chain Commands

cast chain-id

NAME

cast-chain-id - Get the Ethereum chain ID.

SYNOPSIS

cast chain-id [options]

DESCRIPTION

Get the Ethereum chain ID from the RPC endpoint we are connected to.

OPTIONS

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the chain ID when talking to $RPC:
```
cast chain-id --rpc-url $RPC
```
Get the chain ID when $ETH_RPC_URL is set:
```
cast chain-id
```

cast chain

NAME

cast-chain - Get the symbolic name of the current chain.

SYNOPSIS

cast chain [options]

DESCRIPTION

Get the symbolic chain name from the RPC endpoint we are connected to.

OPTIONS

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the chain name when talking to $RPC:
```
cast chain --rpc-url $RPC
```
Get the chain name when $ETH_RPC_URL is set:
```
cast chain
```

cast client

NAME

cast-client - Get the current client version.

SYNOPSIS

cast client [options]

DESCRIPTION

Get the current client version.

OPTIONS

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the current client version:
```
cast client
```

Transaction Commands

cast publish

NAME

cast-publish - Publish a raw transaction to the network.

SYNOPSIS

cast publish [options] tx

DESCRIPTION

Publish a raw pre-signed transaction to the network.

OPTIONS

Publish Options

--async
--cast-async
Do not wait for a transaction receipt.
Environment: CAST_ASYNC

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

--flashbots
Use the Flashbots RPC URL (https://rpc.flashbots.net).

Common Options

-h
--help
Prints help information.

EXAMPLES

Publish a pre-signed transaction:
```
cast publish --rpc-url $RPC $TX
```
Publish a pre-signed transaction with flashbots.
```
cast publish --flashbots $TX
```

cast receipt

NAME

cast-receipt - Get the transaction receipt for a transaction.

SYNOPSIS

cast receipt [options] tx_hash [field]

DESCRIPTION

Get the transaction receipt for a transaction.

If field is specified, then only the given field of the receipt is displayed.

OPTIONS

Receipt Options

--async
--cast-async
Do not wait for the transaction receipt if it does not exist yet.
Environment: CAST_ASYNC

-c confirmations
--confirmations confirmations
Wait a number of confirmations before exiting. Default: 1.

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Display Options

-j
--json
Print the deployment information as JSON.

Common Options

-h
--help
Prints help information.

EXAMPLES

Get a transaction receipt:
```
cast receipt $TX_HASH
```
Get the block number the transaction was included in:
```
cast receipt $TX_HASH blockNumber
```

cast send

NAME

cast-send - Sign and publish a transaction.

SYNOPSIS

cast send [options] to [sig] [args...]

DESCRIPTION

Sign and publish a transaction.

The destination (to) can be an ENS name or an address.

The signature (sig) can be:

A fragment: someFunction(uint256,bytes32)
A selector and encoded calldata: 0xcdba2fd40000000000000000000000000000000000000000000000000000000000007a69
Only the function name: in this case Cast will try to fetch the function signature from Etherscan

OPTIONS

Transaction Options

--gas-limit gas_limit
Gas limit for the transaction.

--gas-price price
Gas price for the transaction, or max fee per gas for EIP1559 transactions.

--priority-gas-price price
Max priority fee per gas for EIP1559 transactions.

--value value
Ether to send in the transaction.

    Either specified as an integer (wei), or as a string with a unit, for example:
    - 1ether
    - 10gwei
    - 0.01ether

--nonce nonce
Nonce for the transaction.

--legacy
Send a legacy transaction instead of an EIP1559 transaction.

This is automatically enabled for common networks without EIP1559.

--resend
Reuse the latest nonce of the sending account.

--create code [sig args...]
Deploy a contract by specifying raw bytecode, in place of specifying a to address.

Receipt Options

--async
--cast-async
Do not wait for the transaction receipt if it does not exist yet.
Environment: CAST_ASYNC

-c confirmations
--confirmations confirmations
Wait a number of confirmations before exiting. Default: 1.

WALLET OPTIONS - RAW:

-i
--interactive <NUM>
Open an interactive prompt to enter your private key. Takes a value for the number of keys to enter.
Defaults to 0.

--mnemonic-derivation-path <PATHS>
The wallet derivation path. Works with both --mnemonic-path and hardware wallets.

--mnemonic-indexes <INDEXES>
Use the private key from the given mnemonic index. Used with --mnemonic-paths.
Defaults to 0.

--mnemonic-passphrase <PASSPHRASE>
Use a BIP39 passphrases for the mnemonic.

--mnemonic <PATHS>
Use the mnemonic phrases or mnemonic files at the specified paths.

--private-key <RAW_PRIVATE_KEY>
Use the provided private key.

--private-keys <RAW_PRIVATE_KEYS>
Use the provided private keys.

Wallet Options - Keystore

--keystore path
Use the keystore in the given folder or file.
Environment: ETH_KEYSTORE

--password password
The keystore password. Used with --keystore.

Wallet Options - Hardware Wallet

-t
--trezor
Use a Trezor hardware wallet.

-l
--ledger
Use a Ledger hardware wallet.

Wallet Options - Remote

-f address
--from address
Sign the transaction with the specified account on the RPC.
Environment: ETH_FROM

--unlocked
Send via eth_sendTransaction using the --from argument or $ETH_FROM as sender.

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

--flashbots
Use the Flashbots RPC URL (https://rpc.flashbots.net).

Etherscan Options

--chain chain_name
The Etherscan chain.

--etherscan-api-key key
Etherscan API key, or the key of an Etherscan configuration table.
Environment: ETHERSCAN_API_KEY

Display Options

-j
--json
Print the deployment information as JSON.

Common Options

-h
--help
Prints help information.

EXAMPLES

Send some ether to Vitalik using your Ledger:

cast send --ledger vitalik.eth --value 0.1ether

Call deposit(address token, uint256 amount) on a contract:

cast send --ledger 0x... "deposit(address,uint256)" 0x... 1

Call a function that expects a struct:

contract Test {
    struct MyStruct {
        address addr;
        uint256 amount;
    }
    function myfunction(MyStruct memory t) public pure {}
}

Structs are encoded as tuples (see struct encoding)

cast send 0x... "myfunction((address,uint256))" "(0x...,1)"

cast call

NAME

cast-call - Perform a call on an account without publishing a transaction.

SYNOPSIS

cast call [options] to sig [args...]

DESCRIPTION

Perform a call on an account without publishing a transaction.

The destination (to) can be an ENS name or an address.

The signature (sig) can be:

A fragment: someFunction(uint256,bytes32)
A selector and encoded calldata: 0xcdba2fd40000000000000000000000000000000000000000000000000000000000007a69
Only the function name: in this case Cast will try to fetch the function signature from Etherscan

OPTIONS

Query Options

-B block
--block block
The block height you want to query at.

Can be a block number, or any of the tags: earliest, finalized, safe, latest or pending.

WALLET OPTIONS - RAW:

-i
--interactive <NUM>
Open an interactive prompt to enter your private key. Takes a value for the number of keys to enter.
Defaults to 0.

--mnemonic-derivation-path <PATHS>
The wallet derivation path. Works with both --mnemonic-path and hardware wallets.

--mnemonic-indexes <INDEXES>
Use the private key from the given mnemonic index. Used with --mnemonic-paths.
Defaults to 0.

--mnemonic-passphrase <PASSPHRASE>
Use a BIP39 passphrases for the mnemonic.

--mnemonic <PATHS>
Use the mnemonic phrases or mnemonic files at the specified paths.

--private-key <RAW_PRIVATE_KEY>
Use the provided private key.

--private-keys <RAW_PRIVATE_KEYS>
Use the provided private keys.

Wallet Options - Keystore

--keystore path
Use the keystore in the given folder or file.
Environment: ETH_KEYSTORE

--password password
The keystore password. Used with --keystore.

Wallet Options - Hardware Wallet

-t
--trezor
Use a Trezor hardware wallet.

-l
--ledger
Use a Ledger hardware wallet.

Wallet Options - Remote

-f address
--from address
Sign the transaction with the specified account on the RPC.
Environment: ETH_FROM

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

--flashbots
Use the Flashbots RPC URL (https://rpc.flashbots.net).

Etherscan Options

--chain chain_name
The Etherscan chain.

--etherscan-api-key key
Etherscan API key, or the key of an Etherscan configuration table.
Environment: ETHERSCAN_API_KEY

Common Options

-h
--help
Prints help information.

EXAMPLES

Call balanceOf(address) on the WETH contract:

cast call 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2 \
  "balanceOf(address)(uint256)" 0x...

Call tokenURI(uint256)(string) on the Tubby Cats NFT contract:

export CONTRACT=0xca7ca7bcc765f77339be2d648ba53ce9c8a262bd
export TOKEN_ID=19938
cast call $CONTRACT "tokenURI(uint256)(string)" $TOKEN_ID

Call getAmountsOut(uint,address[]) on the Uniswap v2 router contract:

cast call 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D \
 "getAmountsOut(uint,address[])" 1 "[0x6b...0f,0xc0...c2]"

cast rpc

NAME

cast-rpc - Perform a raw JSON-RPC request

SYNOPSIS

cast rpc [options] METHOD [PARAMS...]

DESCRIPTION

Perform a simple JSON-RPC POST request for the given method and with the params

OPTIONS

Query Options

-r url
--rpc-url url
The URL of the provider

-w
--raw
Pass the "params" as is If --raw is passed the first PARAM will be taken as the value of "params". If no params are given, stdin will be used. For example: rpc eth_getBlockByNumber '["0x123", false]' --raw => {"method": "eth_getBlockByNumber", "params": ["0x123", false] ... }

EXAMPLES

Get latest eth_getBlockByNumber on localhost:

cast rpc eth_getBlockByNumber "latest" "false"

Get eth_getTransactionByHash on localhost:

cast rpc eth_getTransactionByHash 0x2642e960d3150244e298d52b5b0f024782253e6d0b2c9a01dd4858f7b4665a3f

Get latest eth_getBlockByNumber on etherum mainnet:

cast rpc --rpc-url https://mainnet.infura.io/v3/ eth_getBlockByNumber "latest" "false"

cast tx

NAME

cast-tx - Get information about a transaction.

SYNOPSIS

cast tx [options] tx_hash [field]

DESCRIPTION

Get information about a transaction.

If field is specified, then only the given field of the transaction is displayed.

OPTIONS

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Display Options

-j
--json
Print the deployment information as JSON.

Common Options

-h
--help
Prints help information.

EXAMPLES

Get information about a transaction:
```
cast tx $TX_HASH
```
Get the sender of a transaction:
```
cast tx $TX_HASH from
```

cast run

NAME

cast-run - Runs a published transaction in a local environment and prints the trace.

SYNOPSIS

cast run [options] --rpc-url url tx_hash

DESCRIPTION

Runs a published transaction in a local environment and prints the trace.

By default, all transactions in the block prior to the transaction you want to replay are also replayed. If you want a quicker result, you can use --quick, however, results may differ from the live execution.

You can also open the transaction in a debugger by passing --debug.

OPTIONS

Run Options

--label label
Labels an address in the trace.
The format is <address>:<label>. Can be passed multiple times.

-q
--quick
Executes the transaction only with the state from the previous block.
May result in different results than the live execution!

-v
--verbose
Addresses are fully displayed instead of being truncated.

-d
--debug
Open the script in the debugger.

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Common Options

-h
--help
Prints help information.

EXAMPLES

Replay a transaction (a simple transfer):

cast run 0xd15e0237413d7b824b784e1bbc3926e52f4726e5e5af30418803b8b327b4f8ca

Replay a transaction, applied on top of the state of the previous block:

cast run --quick \
  0xd15e0237413d7b824b784e1bbc3926e52f4726e5e5af30418803b8b327b4f8ca

Replay a transaction with address labels:

cast run \
  --label 0xc564ee9f21ed8a2d8e7e76c085740d5e4c5fafbe:sender \
  --label 0x40950267d12e979ad42974be5ac9a7e452f9505e:recipient \
  --label 0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2:weth \
  0xd15e0237413d7b824b784e1bbc3926e52f4726e5e5af30418803b8b327b4f8ca

Replay a transaction in the debugger:

cast run --debug \
  0xd15e0237413d7b824b784e1bbc3926e52f4726e5e5af30418803b8b327b4f8ca

cast estimate

NAME

cast-estimate - Estimate the gas cost of a transaction.

SYNOPSIS

cast estimate [options] to sig [args...]

DESCRIPTION

Estimate the gas cost of a transaction.

The destination (to) can be an ENS name or an address.

The signature (sig) can be:

A fragment: someFunction(uint256,bytes32)
A selector and encoded calldata: 0xcdba2fd40000000000000000000000000000000000000000000000000000000000007a69
Only the function name: in this case Cast will try to fetch the function signature from Etherscan

OPTIONS

Transaction Options

--value value
Ether to send in the transaction.

    Either specified as an integer (wei), or as a string with a unit, for example:
    - 1ether
    - 10gwei
    - 0.01ether

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

--flashbots
Use the Flashbots RPC URL (https://rpc.flashbots.net).

Etherscan Options

--chain chain_name
The Etherscan chain.

--etherscan-api-key key
Etherscan API key, or the key of an Etherscan configuration table.
Environment: ETHERSCAN_API_KEY

Common Options

-h
--help
Prints help information.

EXAMPLES

Estimate the gas cost of calling deposit() on the WETH contract:

cast estimate 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2 \
  --value 0.1ether "deposit()"

cast access-list

NAME

cast-access-list - Create an access list for a transaction.

SYNOPSIS

cast access-list [options] to sig [args...]

DESCRIPTION

Create an access list for a transaction.

The destination (to) can be an ENS name or an address.

The signature (sig) can be:

A fragment: someFunction(uint256,bytes32)
A selector and encoded calldata: 0xcdba2fd40000000000000000000000000000000000000000000000000000000000007a69
Only the function name: in this case Cast will try to fetch the function signature from Etherscan

OPTIONS

Query Options

-B block
--block block
The block height you want to query at.

Can be a block number, or any of the tags: earliest, finalized, safe, latest or pending.

WALLET OPTIONS - RAW:

-i
--interactive <NUM>
Open an interactive prompt to enter your private key. Takes a value for the number of keys to enter.
Defaults to 0.

--mnemonic-derivation-path <PATHS>
The wallet derivation path. Works with both --mnemonic-path and hardware wallets.

--mnemonic-indexes <INDEXES>
Use the private key from the given mnemonic index. Used with --mnemonic-paths.
Defaults to 0.

--mnemonic-passphrase <PASSPHRASE>
Use a BIP39 passphrases for the mnemonic.

--mnemonic <PATHS>
Use the mnemonic phrases or mnemonic files at the specified paths.

--private-key <RAW_PRIVATE_KEY>
Use the provided private key.

--private-keys <RAW_PRIVATE_KEYS>
Use the provided private keys.

Wallet Options - Keystore

--keystore path
Use the keystore in the given folder or file.
Environment: ETH_KEYSTORE

--password password
The keystore password. Used with --keystore.

Wallet Options - Hardware Wallet

-t
--trezor
Use a Trezor hardware wallet.

-l
--ledger
Use a Ledger hardware wallet.

Wallet Options - Remote

-f address
--from address
Sign the transaction with the specified account on the RPC.
Environment: ETH_FROM

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

--flashbots
Use the Flashbots RPC URL (https://rpc.flashbots.net).

Etherscan Options

--chain chain_name
The Etherscan chain.

--etherscan-api-key key
Etherscan API key, or the key of an Etherscan configuration table.
Environment: ETHERSCAN_API_KEY

Common Options

-h
--help
Prints help information.

Block Commands

cast find-block

NAME

cast-find-block - Get the block number closest to the provided timestamp.

SYNOPSIS

cast find-block [options] timestamp

DESCRIPTION

Get the block number closest to the provided timestamp.

OPTIONS

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the block number closest to New Years 2021
```
cast find-block 1609459200
```

cast gas-price

NAME

cast-gas-price - Get the current gas price.

SYNOPSIS

cast gas-price [options]

DESCRIPTION

Get the current gas price.

OPTIONS

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the current gas price:
```
cast gas-price
```

cast block-number

NAME

cast-block-number - Get the latest block number.

SYNOPSIS

cast block-number [options]

DESCRIPTION

Get the latest block number.

OPTIONS

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the latest block number:
```
cast block-number
```

cast basefee

NAME

cast-base-fee - Get the basefee of a block.

SYNOPSIS

cast base-fee [options] [block]

DESCRIPTION

Get the basefee of a block.

The specified block can be a block number, or any of the tags: earliest, finalized, safe, latest or pending. Default to latest.

OPTIONS

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the basefee of the latest block:
```
cast base-fee
```
Get the basefee of the genesis block:
```
cast base-fee 1
```

cast block

NAME

cast-block - Get information about a block.

SYNOPSIS

cast block [options] [block]

DESCRIPTION

Get information about a block.

The specified block can be a block number, or any of the tags: earliest, finalized, safe, latest or pending. Default to latest.

OPTIONS

-f field
--field field
If specified, only get the given field of the block.

Display Options

-j
--json
Print the deployment information as JSON.

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the latest block:
```
cast block
```
Get the finalized block:
```
cast block finalized
```
Get the hash of the latest block:
```
cast block latest -f hash
```

cast age

NAME

cast-age - Get the timestamp of a block.

SYNOPSIS

cast age [options] [block]

DESCRIPTION

Get the timestamp of a block.

The specified block can be a block number, or any of the tags: earliest, finalized, safe, latest or pending. Default to latest.

OPTIONS

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the timestamp of the latest block:
```
cast age
```
Get the timestamp of the genesis block:
```
cast age 1
```

Account Commands

cast balance

NAME

cast-balance - Get the balance of an account in wei.

SYNOPSIS

cast balance [options] who

DESCRIPTION

Get the balance of an account.

The argument who can be an ENS name or an address.

OPTIONS

Query Options

-B block
--block block
The block height you want to query at.

Can be a block number, or any of the tags: earliest, finalized, safe, latest or pending.

-e ether
--ether ether
If this flag is used then balance will be shown in ether

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the balance of beer.eth
```
cast balance beer.eth
```

cast storage

NAME

cast-storage - Get the raw value of a contract's storage slot or its full storage layout.

SYNOPSIS

cast storage [options] address slot

DESCRIPTION

Get the raw value of a contract's storage slot. (Slot locations greater than 18446744073709551615 (u64::MAX) should be given as hex. Use cast index to compute mapping slots.)

Emit the slot number to get the full storage layout (requires contract to be verified on Etherscan with a Solidity version > 0.6.5 or you must be in a Forge project with a local contract matching the deployed bytecode).

The address (address) can be an ENS name or an address.

OPTIONS

Query Options

-B block --block block The block height you want to query at.

Can be a block number, or any of the tags: earliest, finalized, safe, latest or pending.

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the value of slot 0 on the WETH contract.

cast storage 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2 0

Get the full storage layout of the Milady contract.

cast storage 0x5Af0D9827E0c53E4799BB226655A1de152A425a5

cast proof

NAME

cast-proof - Generate a storage proof for a given storage slot.

SYNOPSIS

cast proof [options] address [slots...]

DESCRIPTION

Generate a storage proof for a given storage slot.

The address (address) can be an ENS name or an address.

The displayed output is a JSON object with the following keys:

accountProof: Proof for the account itself
address: The address of the account
balance: The balance of the account
codeHash: A hash of the account's code
nonce: The nonce of the account
storageHash: A hash of the account's storage
storageProof: An array of storage proofs, one for each requested slot
storageProof.key: The slot
storageProof.proof: The proof for the slot
storageProof.value: The value of the slot

OPTIONS

Query Options

-B block
--block block
The block height you want to query at.

Can be a block number, or any of the tags: earliest, finalized, safe, latest or pending.

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Display Options

-j
--json
Print the deployment information as JSON.

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the proof for storage slot 0 on the WETH contract:

cast proof 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2 0

cast nonce

NAME

cast-nonce - Get the nonce for an account.

SYNOPSIS

cast nonce [options] who

DESCRIPTION

Get the nonce of an account.

The argument who can be an ENS name or an address.

OPTIONS

Query Options

-B block
--block block
The block height you want to query at.

Can be a block number, or any of the tags: earliest, finalized, safe, latest or pending.

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the nonce of beer.eth
```
cast nonce beer.eth
```

cast code

NAME

cast-code - Get the bytecode of a contract.

SYNOPSIS

cast code [options] address

DESCRIPTION

Get the bytecode of a contract.

The contract (address) can be an ENS name or an address.

OPTIONS

Query Options

-B block
--block block
The block height you want to query at.

Can be a block number, or any of the tags: earliest, finalized, safe, latest or pending.

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the bytecode of the WETH contract.

cast code 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2

cast codesize

NAME

cast-codesize - Get the runtime bytecode size of a contract.

SYNOPSIS

cast codesize [options] address

DESCRIPTION

Get the runtime bytecode size of a contract.

The contract (address) can be an ENS name or an address.

OPTIONS

Query Options

-B block
--block block
The block height you want to query at.

Can be a block number, or any of the tags: earliest, finalized, safe, latest or pending.

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the runtime bytecode size of the WETH contract.

cast codesize 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2

ENS Commands

cast lookup-address

NAME

cast-lookup-address - Perform an ENS reverse lookup.

SYNOPSIS

cast lookup-address [options] who

DESCRIPTION

Perform an ENS reverse lookup.

If --verify is passed, then a normal lookup is performed after the reverse lookup to verify that the address is correct.

OPTIONS

Lookup Options

-v
--verify
Perform a normal lookup to verify that the address is correct.

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the ENS name for an address.
```
cast lookup-address $ADDRESS
```
Perform both a reverse and a normal lookup:
```
cast lookup-address --verify $ADDRESS
```

cast resolve-name

NAME

cast-resolve-name - Perform an ENS lookup.

SYNOPSIS

cast resolve-name [options] who

DESCRIPTION

Perform an ENS lookup.

If --verify is passed, then a reverse lookup is performed after the normal lookup to verify that the name is correct.

OPTIONS

Lookup Options

-v
--verify
Perform a reverse lookup to verify that the name is correct.

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the address for an ENS name.
```
cast resolve-name vitalik.eth
```
Perform both a normal and a reverse lookup:
```
cast resolve-name --verify vitalik.eth
```

cast namehash

NAME

cast-namehash - Calculate the ENS namehash of a name.

SYNOPSIS

cast namehash [options] name

DESCRIPTION

Calculate the ENS namehash of a name.

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Calculate the namehash of an ENS name.
```
cast namehash vitalik.eth
```

Etherscan Commands

cast etherscan-source

cast etherscan-source

NAME

cast-etherscan-source - Get the source code of a contract from Etherscan.

SYNOPSIS

cast etherscan-source [options] address

DESCRIPTION

Get the source code of a contract from Etherscan.

The destination (to) can be an ENS name or an address.

OPTIONS

Output Options

-d directory
The output directory to expand the source tree into. If not provided, the source will be outputted to stdout.

Etherscan Options

--chain chain_name
The Etherscan chain.

--etherscan-api-key key
Etherscan API key, or the key of an Etherscan configuration table.
Environment: ETHERSCAN_API_KEY

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the source code of the WETH contract:

cast etherscan-source 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2

Expand the source code of the WETH contract into a directory named weth

cast etherscan-source -d weth 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2

ABI Commands

cast abi-encode

NAME

cast-abi-encode - ABI encode the given function arguments, excluding the selector.

SYNOPSIS

cast abi-encode [options] sig [args...]

DESCRIPTION

ABI encode the given function, excluding the selector.

The signature (sig) is a fragment in the form <function name>(<types...>).

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

ABI-encode the arguments for a call to someFunc(address,uint256):
```
cast abi-encode "someFunc(address,uint256)" 0x... 1
```
For encoding a type with components (as a tuple, or custom struct):
```
cast abi-encode "someFunc((string,uint256))" "(myString,1)"
```

cast 4byte

NAME

cast-4byte - Get the function signatures for the given selector from https://sig.eth.samczsun.com.

SYNOPSIS

cast 4byte [options] sig

DESCRIPTION

Get the function signatures for the given selector from https://sig.eth.samczsun.com.

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the function signature for the selector 0x8cc5ce99:
```
cast 4byte 0x8cc5ce99
```

cast 4byte-decode

NAME

cast-4byte-decode - Decode ABI-encoded calldata using https://sig.eth.samczsun.com.

SYNOPSIS

cast 4byte-decode [options] calldata

DESCRIPTION

Decode ABI-encoded calldata using https://sig.eth.samczsun.com.

OPTIONS

4byte Options

--id id
    The index of the resolved signature to use.
    https://sig.eth.samczsun.com can have multiple possible signatures for a given selector.
    The index can be an integer, or the tags "earliest" and "latest".

Common Options

-h
--help
Prints help information.

EXAMPLES

Decode calldata for a transfer call:

cast 4byte-decode 0xa9059cbb000000000000000000000000e78388b4ce79068e89bf8aa7f218ef6b9ab0e9d00000000000000000000000000000000000000000000000000174b37380cea000

cast 4byte-event

NAME

cast-4byte-event - Get the event signature for a given topic 0 from https://sig.eth.samczsun.com.

SYNOPSIS

cast 4byte-event [options] topic_0

DESCRIPTION

Get the event signature for a given topic 0 from https://sig.eth.samczsun.com.

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the event signature for a topic 0 of 0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef:
```
cast 4byte-event 0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef
```

cast calldata

NAME

cast-calldata - ABI-encode a function with arguments.

SYNOPSIS

cast calldata [options] sig [args...]

DESCRIPTION

ABI-encode a function with arguments.

The signature (sig) is a fragment in the form <function name>(<types...>).

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

ABI-encode the arguments for a call to someFunc(address,uint256):
```
cast calldata "someFunc(address,uint256)" 0x... 1
```

cast pretty-calldata

NAME

cast-pretty-calldata - Pretty print calldata.

SYNOPSIS

cast pretty-calldata [options] calldata

DESCRIPTION

Pretty print calldata.

Tries to decode the calldata using https://sig.eth.samczsun.com unless --offline is passed.

OPTIONS

4byte Options

-o
--offline
Skip the https://sig.eth.samczsun.com lookup.

Common Options

-h
--help
Prints help information.

EXAMPLES

Decode calldata for a transfer call:

cast pretty-calldata 0xa9059cbb000000000000000000000000e78388b4ce79068e89bf8aa7f218ef6b9ab0e9d00000000000000000000000000000000000000000000000000174b37380cea000

cast --abi-decode

NAME

cast---abi-decode - Decode ABI-encoded input or output data.

SYNOPSIS

cast --abi-decode [options] sig calldata

DESCRIPTION

Decode ABI-encoded input or output data.

By default, the command will decode output data. To decode input data, pass --input or use cast --calldata-decode.

The signature (sig) is a fragment in the form <function name>(<types...>)(<types...>).

OPTIONS

Decoder Options

-i
--input
Decode input data.

Common Options

-h
--help
Prints help information.

EXAMPLES

Decode output data for a balanceOf call:

cast --abi-decode "balanceOf(address)(uint256)" \
  0x000000000000000000000000000000000000000000000000000000000000000a

Decode input data for a transfer call:

cast --abi-decode --input "transfer(address,uint256)" \
  0xa9059cbb000000000000000000000000e78388b4ce79068e89bf8aa7f218ef6b9ab0e9d0000000000000000000000000000000000000000000000000008a8e4b1a3d8000

cast --calldata-decode

NAME

cast---calldata-decode - Decode ABI-encoded input data.

SYNOPSIS

cast --calldata-decode [options] sig calldata

DESCRIPTION

Decode ABI-encoded input data.

The signature (sig) is a fragment in the form <function name>(<types...>).

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Decode input data for a transfer call:

cast --calldata-decode "transfer(address,uint256)" \
  0xa9059cbb000000000000000000000000e78388b4ce79068e89bf8aa7f218ef6b9ab0e9d0000000000000000000000000000000000000000000000000008a8e4b1a3d8000

cast upload-signature

NAME

cast-upload-signature

SYNOPSIS

cast upload-signature [signatures...]

DESCRIPTION

Upload the given signatures to https://sig.eth.samczsun.com.

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Upload signatures

cast upload-signature 'function approve(address,uint256)' \
'transfer(uint256)' 'event Transfer(uint256,address)'

Conversion Commands

cast --format-bytes32-string

NAME

cast---format-bytes32-string - Formats a string into bytes32 encoding.

SYNOPSIS

cast --format-bytes32-string [options] string

DESCRIPTION

Formats a string into bytes32 encoding.

Note that this command is for formatting a Solidity string literal into bytes32 only. If you're looking to pad a byte string, use --to-bytes32 instead.

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Turn string "hello" into bytes32 hex:
```
cast --format-bytes32-string "hello"
```

cast --from-bin

NAME

cast---from-bin - Convert binary data into hex data.

SYNOPSIS

cast --from-bin [options]

DESCRIPTION

Convert binary data into hex data.

The input is taken from stdin.

OPTIONS

Common Options

-h
--help
Prints help information.

cast --from-fix

NAME

cast---from-fix - Convert a fixed point number into an integer.

SYNOPSIS

cast --from-fix [options] decimals value

DESCRIPTION

Convert a fixed point number into an integer.

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Convert 10.55 to an integer:
```
cast --from-fix 2 10.55
```

cast --from-rlp

NAME

cast---from-rlp - Decodes RLP-encoded data.

SYNOPSIS

cast --from-rlp data

DESCRIPTION

Decodes RLP-encoded data.

The data is a hexadecimal string with optional 0x prefix.

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Decode RLP data:

cast --from-rlp 0xc481f181f2

cast --from-rlp c481f181f2

cast --from-utf8

NAME

cast---from-utf8 - Convert UTF8 text to hex.

SYNOPSIS

cast --from-utf8 [options] text

DESCRIPTION

Convert UTF8 text to hex.

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Convert UTF8 text to hex:
```
cast --from-utf8 "hello"
```

cast --parse-bytes32-string

NAME

cast---parse-bytes32-string - Parses a string from bytes32 encoding.

SYNOPSIS

cast --parse-bytes32-string [options] bytes

DESCRIPTION

Parses a Solidity string literal from its bytes32 encoding representation mostly by interpreting bytes as ASCII characters. This command undos the encoding in --format-bytes32-string.

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Parse bytes32 string encoding of "hello" back to the string representation:

cast --parse-bytes32-string "0x68656c6c6f000000000000000000000000000000000000000000000000000000"

cast --to-ascii

NAME

cast---to-ascii - Convert hex data to an ASCII string.

SYNOPSIS

cast --to-ascii [options] text

DESCRIPTION

Convert hex data to an ASCII string.

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Convert hex data to an ASCII string:
```
cast --to-ascii "0x68656c6c6f"
```

cast --to-base

NAME

cast---to-base - Convert a number of one base to another.

SYNOPSIS

cast --to-base [options] value base

DESCRIPTION

Convert a number of one base to another.

OPTIONS

Base Options

--base-in base The base of the input number. Available options:

10, d, dec, decimal

16, h, hex, hexadecimal

Common Options

-h
--help
Prints help information.

EXAMPLES

Convert the decimal number 64 to hexadecimal
```
cast --to-base 64 hex
```
Convert the hexadecimal number 100 to binary
```
cast --to-base 0x100 2
```

Note: The --base-in parameter is not enforced but will be needed if the input is ambiguous.

cast --to-bytes32

NAME

cast---to-bytes32 - Right-pads hex data to 32 bytes.

SYNOPSIS

cast --to-bytes32 [options] bytes

DESCRIPTION

Right-pads hex data to 32 bytes.

Note that this command is for padding a byte string only. If you're looking to format a Solidity string literal into bytes32, use --format-bytes32-string instead.

OPTIONS

Common Options

-h
--help
Prints help information.

cast --to-fix

NAME

cast---to-fix - Convert an integer into a fixed point number.

SYNOPSIS

cast --to-fix [options] decimals value

DESCRIPTION

Convert an integer into a fixed point number.

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Convert 250 to a fixed point number with 2 decimals:
```
cast --to-fix 2 250
```

cast --to-hexdata

NAME

cast---to-hexdata - Normalize the input to lowercase, 0x-prefixed hex.

SYNOPSIS

cast --to-hexdata [options] input

DESCRIPTION

Normalize the input to lowercase, 0x-prefixed hex.

The input data (input) can either be:

Mixed case hex with or without the 0x prefix.
0x prefixed hex that should be concatenated, separated by :.
An absolute path to a file containing hex.
A @tag, where the tag is defined in an environment variable.

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Add 0x prefix:
```
cast --to-hexdata deadbeef
```
Concatenate hex values:
```
cast --to-hexdata "deadbeef:0xbeef"
```
Normalize hex value in MY_VAR:
```
cast --to-hexdata "@MY_VAR"
```

cast --to-int256

NAME

cast---to-int256 - Convert a number to a hex-encoded int256.

SYNOPSIS

cast --to-int256 [options] value

DESCRIPTION

Convert a number to a hex-encoded int256.

OPTIONS

Common Options

-h
--help
Prints help information.

cast --to-rlp

NAME

cast---to-rlp - Encodes hex data to RLP.

SYNOPSIS

cast --to-rlp array

DESCRIPTION

RLP encodes a hex string or a JSON array of hex strings.

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Encoding RLP data:

cast --to-rlp '["0xaa","0xbb","cc"]'

cast --to-rlp f0a9

cast --to-uint256

NAME

cast---to-uint256 - Convert a number to a hex-encoded uint256.

SYNOPSIS

cast --to-uint256 [options] value

DESCRIPTION

Convert a number to a hex-encoded uint256.

OPTIONS

Common Options

-h
--help
Prints help information.

cast --to-unit

NAME

cast---to-unit - Convert an eth amount to another unit.

SYNOPSIS

cast --to-unit [options] value [unit]

DESCRIPTION

Convert an eth amount to another unit.

The value to convert (value) can be a quantity of eth (in wei), or a number with a unit attached to it.

Valid units are:

ether
gwei
wei

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Convert 1000 wei to gwei
```
cast --to-unit 1000 gwei
```
Convert 1 eth to gwei
```
cast --to-unit 1ether gwei
```

cast --to-wei

NAME

cast---to-wei - Convert an eth amount to wei.

SYNOPSIS

cast --to-wei [options] value [unit]

DESCRIPTION

Convert an eth amount to wei.

Consider using cast --to-unit.

OPTIONS

Common Options

-h
--help
Prints help information.

cast shl

NAME

cast-shl - Perform a left shifting operation.

SYNOPSIS

cast shl [options] value shift

DESCRIPTION

Perform a left shifting operation.

OPTIONS

Base Options

--base-in base The base of the input number. Available options:

10, d, dec, decimal

16, h, hex, hexadecimal

--base-out base The desired base of the output. Available options:

2, b, bin, binary

8, o, oct, octal

10, d, dec, decimal

16, h, hex, hexadecimal

Common Options

-h
--help
Prints help information.

EXAMPLES

Perform a 3 position left bit shift of the number 61
```
cast shl --base-in 10 61 3
```

Note: The --base-in parameter is not enforced but will be needed if the input is ambiguous.

cast shr

NAME

cast-shr - Perform a right shifting operation.

SYNOPSIS

cast shr [options] value shift

DESCRIPTION

Perform a left shifting operation.

OPTIONS

Base Options

--base-in base The base of the input number. Available options:

10, d, dec, decimal

16, h, hex, hexadecimal

--base-out base The desired base of the output. Available options:

2, b, bin, binary

8, o, oct, octal

10, d, dec, decimal

16, h, hex, hexadecimal

Common Options

-h
--help
Prints help information.

EXAMPLES

Perform a single right bit shift of 0x12
```
cast shr --base-in 16 0x12 1
```

Note: The --base-in parameter is not enforced but will be needed if the input is ambiguous.

Utility Commands

cast sig

NAME

cast-sig - Get the selector for a function.

SYNOPSIS

cast sig [options] sig

DESCRIPTION

Get the selector for a function.

The signature (sig) is a fragment in the form <function name>(<types...>).

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the selector for the function transfer(address,uint256):
```
cast sig "transfer(address,uint256)"
```

Get the selector for a function that expects a struct:

contract Test {
    struct MyStruct {
        address addr;
        uint256 amount;
    }
    function myfunction(MyStruct memory t) public pure {}
}

Structs are encoded as tuples (see struct encoding).

cast sig "myfunction((address,uint256))"

cast sig-event

NAME

cast-sig-event - Generate event signatures from event string.

SYNOPSIS

cast sig-event [options] event_string

DESCRIPTION

Generate event signatures from event string.

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the hash for the log Transfer(address indexed from, address indexed to, uint256 amount):
```
cast sig-event "Transfer(address indexed from, address indexed to, uint256 amount)"
```

cast keccak

NAME

cast-keccak - Hash arbitrary data using keccak-256.

SYNOPSIS

cast keccak [options] data

DESCRIPTION

Hash arbitrary data using keccak-256.

OPTIONS

Common Options

-h
--help
Prints help information.

cast compute-address

NAME

cast-compute-address - Compute the contract address from a given nonce and deployer address.

SYNOPSIS

cast compute-address [options] address

DESCRIPTION

Compute the contract address from a given nonce and deployer address.

OPTIONS

Compute Options

--nonce nonce
The nonce of the account. Defaults to the latest nonce, fetched from the RPC.

RPC Options

--rpc-url url
The RPC endpoint. Accepts a URL or an existing alias in the [rpc_endpoints] table, like mainnet. Environment: ETH_RPC_URL

Common Options

-h
--help
Prints help information.

cast create2

NAME

cast-create2 - Generate a deterministic contract address using CREATE2

SYNOPSIS

cast create2 [options]

DESCRIPTION

Generate a deterministic contract address using CREATE2

OPTIONS

Common Options

-h
--help
Prints help information.

cast interface

NAME

cast-interface - Generate a Solidity interface from a given ABI.

SYNOPSIS

cast interface [options] address_or_path

DESCRIPTION

Generates a Solidity interface from a given ABI.

The argument (address_or_path) can either be the path to a file containing an ABI, or an address.

If an address is provided, then the interface is generated from the ABI of the account, which is fetched from Etherscan.

ℹ️ Note

This command does not currently support ABI encoder v2.

OPTIONS

Interface Options

-n name
--name name
The name to use for the generated interface. The default name is Interface.

-o path
The path to the output file. If not specified, the interface will be output to stdout.

-p version
--pragma version
The Solidity pragma version to use in the interface. Default: ^0.8.10.

Etherscan Options

--chain chain_name
The Etherscan chain.

--etherscan-api-key key
Etherscan API key, or the key of an Etherscan configuration table.
Environment: ETHERSCAN_API_KEY

Common Options

-h
--help
Prints help information.

EXAMPLES

Generate an interface from a file:
```
cast interface ./path/to/abi.json
```

Generate an interface using Etherscan:

cast interface -o IWETH.sol 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2

Generate and name an interface from a file:

cast interface -n LilENS ./path/to/abi.json

cast index

NAME

cast-index - Compute the storage slot location for an entry in a mapping.

SYNOPSIS

cast index key_type key slot

DESCRIPTION

Compute the storage slot location for an entry in a mapping.

Use cast storage to get the value.

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

// World.sol

mapping (address => uint256) public mapping1;
mapping (string => string) public mapping2;

Compute the storage slot of an entry (hello) in a mapping of type mapping(string => string), located at slot 1:

>> cast index string "hello" 1
0x3556fc8e3c702d4479a1ab7928dd05d87508462a12f53307b5407c969223d1f8
>> cast storage [address] 0x3556fc8e3c702d4479a1ab7928dd05d87508462a12f53307b5407c969223d1f8
world

cast --concat-hex

NAME

cast---concat-hex - Concatenate hex strings.

SYNOPSIS

cast --concat-hex data...

DESCRIPTION

Concatenate hex strings.

OPTIONS

Common Options

-h
--help
Prints help information.

EXAMPLES

Concatenate hex strings:
```
cast --concat-hex 0xa 0xb 0xc
```

cast --max-int

NAME

cast---max-int - Get the maximum i256 value.

SYNOPSIS

cast --max-int

DESCRIPTION

Get the maximum i256 value.

OPTIONS

Common Options

-h
--help
Prints help information.

cast --min-int

NAME

cast---min-int - Get the minimum i256 value.

SYNOPSIS

cast --min-int

DESCRIPTION

Get the minimum i256 value.

OPTIONS

Common Options

-h
--help
Prints help information.

cast --max-uint

NAME

cast---max-uint - Get the maximum uint256 value.

SYNOPSIS

cast --max-uint

DESCRIPTION

Get the maximum uint256 value.

OPTIONS

Common Options

-h
--help
Prints help information.

cast --to-checksum-address

NAME

cast---to-checksum-address - Convert an addresss to a checksummed format (EIP-55).

SYNOPSIS

cast --to-checksum-address address

DESCRIPTION

Convert an addresss to a checksummed format (EIP-55).

OPTIONS

Common Options

-h
--help
Prints help information.

Wallet Commands

cast wallet

NAME

cast-wallet - Wallet management utilities.

SYNOPSIS

cast wallet [options] command [args]
cast wallet [options] --version
cast wallet [options] --help

DESCRIPTION

This program is a set of tools to use, create and manage wallets.

COMMANDS

cast wallet new
Create a new random keypair.

cast wallet address
Convert a private key to an address.

cast wallet sign
Sign a message.

cast wallet vanity
Generate a vanity address.

cast wallet verify
Verify the signature of a message.

OPTIONS

Special Options

-V
--version
Print version info and exit.

Common Options

-h
--help
Prints help information.

cast wallet new

NAME

cast-wallet-new - Create a new random keypair.

SYNOPSIS

cast wallet new [options] [path]

DESCRIPTION

Create a new random keypair.

If path is specified, then the new keypair will be written to a JSON keystore encrypted with a password. (path should be an existing directory.)

OPTIONS

Keystore Options

-p
--password
Triggers a hidden password prompt for the JSON keystore.
Deprecated: prompting for a hidden password is now the default.

--unsafe-password password
Password for the JSON keystore in cleartext.

This is unsafe to use and we recommend using --password instead.
Environment: CAST_PASSWORD

Common Options

-h
--help
Prints help information.

EXAMPLES

Create a new keypair without saving it to a keystore:
```
cast wallet new
```
Create a new keypair and save it in the keystore directory:
```
cast wallet new keystore
```

cast wallet address

NAME

cast-wallet-address - Convert a private key to an address.

SYNOPSIS

cast wallet address [options]

DESCRIPTION

Convert a private key to an address.

OPTIONS

Keystore Options

WALLET OPTIONS - RAW:

-i
--interactive <NUM>
Open an interactive prompt to enter your private key. Takes a value for the number of keys to enter.
Defaults to 0.

--mnemonic-derivation-path <PATHS>
The wallet derivation path. Works with both --mnemonic-path and hardware wallets.

--mnemonic-indexes <INDEXES>
Use the private key from the given mnemonic index. Used with --mnemonic-paths.
Defaults to 0.

--mnemonic-passphrase <PASSPHRASE>
Use a BIP39 passphrases for the mnemonic.

--mnemonic <PATHS>
Use the mnemonic phrases or mnemonic files at the specified paths.

--private-key <RAW_PRIVATE_KEY>
Use the provided private key.

--private-keys <RAW_PRIVATE_KEYS>
Use the provided private keys.

Wallet Options - Keystore

--keystore path
Use the keystore in the given folder or file.
Environment: ETH_KEYSTORE

--password password
The keystore password. Used with --keystore.

Wallet Options - Hardware Wallet

-t
--trezor
Use a Trezor hardware wallet.

-l
--ledger
Use a Ledger hardware wallet.

Common Options

-h
--help
Prints help information.

EXAMPLES

Get the address of the keypair in keystore.json:
```
cast wallet address --keystore keystore.json
```

cast wallet sign

NAME

cast-wallet-sign - Sign a message.

SYNOPSIS

cast wallet sign [options] message

DESCRIPTION

Sign a message.

OPTIONS

WALLET OPTIONS - RAW:

-i
--interactive <NUM>
Open an interactive prompt to enter your private key. Takes a value for the number of keys to enter.
Defaults to 0.

--mnemonic-derivation-path <PATHS>
The wallet derivation path. Works with both --mnemonic-path and hardware wallets.

--mnemonic-indexes <INDEXES>
Use the private key from the given mnemonic index. Used with --mnemonic-paths.
Defaults to 0.

--mnemonic-passphrase <PASSPHRASE>
Use a BIP39 passphrases for the mnemonic.

--mnemonic <PATHS>
Use the mnemonic phrases or mnemonic files at the specified paths.

--private-key <RAW_PRIVATE_KEY>
Use the provided private key.

--private-keys <RAW_PRIVATE_KEYS>
Use the provided private keys.

Wallet Options - Keystore

--keystore path
Use the keystore in the given folder or file.
Environment: ETH_KEYSTORE

--password password
The keystore password. Used with --keystore.

Wallet Options - Hardware Wallet

-t
--trezor
Use a Trezor hardware wallet.

-l
--ledger
Use a Ledger hardware wallet.

Common Options

-h
--help
Prints help information.

EXAMPLES

Sign a message using a keystore:

cast wallet sign --keystore keystore.json --interactive "hello"

Sign a message using a raw private key:

cast wallet sign --private-key $PRIV_KEY "hello"

cast wallet vanity

NAME

cast-wallet-vanity - Generate a vanity address.

SYNOPSIS

cast wallet vanity [options]

DESCRIPTION

Generate a vanity address.

If --nonce is specified, then the command will try to generate a vanity contract address.

OPTIONS

Keystore Options

--starts-with hex
Prefix for the vanity address.

--ends-with hex
Suffix for the vanity address.

--nonce nonce
Generate a vanity contract address created by the generated keypair with the specified nonce.

Common Options

-h
--help
Prints help information.

EXAMPLES

Create a new keypair that starts with dead:
```
cast wallet vanity --starts-with dead
```
Create a new keypair ends with beef:
```
cast wallet vanity --ends-with beef
```

cast wallet verify

NAME

cast-wallet-verify - Verify the signature of a message.

SYNOPSIS

cast wallet verify [options] --address address message signature

DESCRIPTION

Verify the signature of a message.

OPTIONS

Signature Options

-a address
--address address
The address of the message signer.

Common Options

-h
--help
Prints help information.

anvil

NAME

anvil - Create a local testnet node for deploying and testing smart contracts. It can also be used to fork other EVM compatible networks.

SYNOPSIS

anvil [options]

DESCRIPTION

Create a local testnet node for deploying and testing smart contracts. It can also be used to fork other EVM compatible networks.

This section covers an extensive list of information about Mining Modes, Supported Transport Layers, Supported RPC Methods, Anvil flags and their usages. You can run multiple flags at the same time.

Mining Modes

Mining modes refer to how frequent blocks are mined using Anvil. By default, it automatically generates a new block as soon as a transaction is submitted.

You can change this setting to interval mining if you will, which means that a new block will be generated in a given period of time selected by the user. If you want to go for this type of mining, you can do it by adding the --block-time <block-time-in-seconds> flag, like in the following example.

# Produces a new block every 10 seconds
anvil --block-time 10

There's also a third mining mode called never. In this case, it disables auto and interval mining, and mine on demand instead. You can do this by typing:

# Enables never mining mode
anvil --no-mining

Supported Transport Layers

HTTP and Websocket connections are supported. The server listens on port 8545 by default, but it can be changed by running the following command:

anvil --port <PORT>

Supported RPC Methods

Standard Methods

The standard methods are based on this reference.

web3_clientVersion
web3_sha3
eth_chainId
eth_networkId
eth_gasPrice
eth_accounts
eth_blockNumber
eth_getBalance
eth_getStorageAt
eth_getBlockByHash
eth_getBlockByNumber
eth_getTransactionCount
eth_getBlockTransactionCountByHash
eth_getBlockTransactionCountByNumber
eth_getUncleCountByBlockHash
eth_getUncleCountByBlockNumber
eth_getCode
eth_sign
eth_signTypedData_v4
eth_sendTransaction
eth_sendRawTransaction
eth_call
eth_createAccessList
eth_estimateGas
eth_getTransactionByHash
eth_getTransactionByBlockHashAndIndex
eth_getTransactionByBlockNumberAndIndex
eth_getTransactionReceipt
eth_getUncleByBlockHashAndIndex
eth_getUncleByBlockNumberAndIndex
eth_getLogs
eth_newFilter
eth_getFilterChanges
eth_newBlockFilter
eth_newPendingTransactionFilter
eth_getFilterLogs
eth_uninstallFilter
eth_getWork
eth_subscribe
eth_unsubscribe
eth_syncing
eth_submitWork
eth_submitHashrate
eth_feeHistory
eth_getProof
debug_traceTransaction
Use anvil --steps-tracing to get structLogs
debug_traceCall Note that non-standard traces are not yet support. This means you can't pass any arguments to the trace parameter.
trace_transaction
trace_block

Custom Methods

The anvil_* namespace is an alias for hardhat. For more info, refer to the Hardhat documentation.

anvil_impersonateAccount
Send transactions impersonating an externally owned account or contract.

anvil_stopImpersonatingAccount
Stops impersonating an account or contract if previously set with anvil_impersonateAccount

anvil_autoImpersonateAccount
Accepts true to enable auto impersonation of accounts, and false to disable it. When enabled, any transaction's sender will be automatically impersonated. Same as anvil_impersonateAccount.

anvil_getAutomine
Returns true if automatic mining is enabled, and false if it is not

anvil_mine
Mines a series of blocks

anvil_dropTransaction
Removes transactions from the pool

anvil_reset
Reset the fork to a fresh forked state, and optionally update the fork config

anvil_setRpcUrl
Sets the backend RPC URL

anvil_setBalance
Modifies the balance of an account

anvil_setCode
Sets the code of a contract

anvil_setNonce
Sets the nonce of an address

anvil_setStorageAt
Writes a single slot of the account's storage

anvil_setCoinbase
Sets the coinbase address

anvil_setLoggingEnabled
Enable or disable logging

anvil_setMinGasPrice
Set the minimum gas price for the node

anvil_setNextBlockBaseFeePerGas
Sets the base fee of the next block

anvil_dumpState Returns a hex string representing the complete state of the chain. Can be re-imported into a fresh/restarted instance of Anvil to reattain the same state.

anvil_loadState When given a hex string previously returned by anvil_dumpState, merges the contents into the current chain state. Will overwrite any colliding accounts/storage slots.

anvil_nodeInfo Retrieves the configuration params for the currently running Anvil node.

Special Methods

The special methods come from Ganache. You can take a look at the documentation here.

evm_setAutomine
Enables or disables, based on the single boolean argument, the automatic mining of new blocks with each new transaction submitted to the network

evm_setIntervalMining
Sets the mining behavior to interval with the given interval (seconds)

evm_snapshot
Snapshot the state of the blockchain at the current block

evm_revert
Revert the state of the blockchain to a previous snapshot. Takes a single parameter, which is the snapshot id to revert to

evm_increaseTime
Jump forward in time by the given amount of time, in seconds

evm_setNextBlockTimestamp
Similar to evm_increaseTime but takes the exact timestamp that you want in the next block

anvil_setBlockTimestampInterval
Similar to evm_increaseTime but sets a block timestamp interval. The timestamp of the next block will be computed as lastBlock_timestamp + interval

evm_setBlockGasLimit
Sets the block gas limit for the following blocks

anvil_removeBlockTimestampInterval
Removes an anvil_setBlockTimestampInterval if it exists

evm_mine
Mine a single block

anvil_enableTraces
Turn on call traces for transactions that are returned to the user when they execute a transaction (instead of just txhash/receipt)

eth_sendUnsignedTransaction
Execute a transaction regardless of signature status

For the next three methods, make sure to read Geth's documentation.

txpool_status
Returns the number of transactions currently pending for inclusion in the next block(s), as well as the ones that are being scheduled for future execution only

txpool_inspect
Returns a summary of all the transactions currently pending for inclusion in the next block(s), as well as the ones that are being scheduled for future execution only

txpool_content
Returns the details of all transactions currently pending for inclusion in the next block(s), as well as the ones that are being scheduled for future execution only

OPTIONS

General Options

-a, --accounts <ACCOUNTS>
Set the number of accounts [default: 10]

-b, --block-time <block-time>
Block time in seconds for interval mining

--balance <BALANCE>
Set the balance of the accounts [default: 10000]

--derivation-path <DERIVATION_PATH>
Set the derivation path of the child key to be derived [default: m/44'/60'/0'/0/]

-h, --help
Print help information

--hardfork <HARDFORK>
Choose the EVM hardfork to use Choose the hardfork by name, e.g. shanghai, paris, london, etc... [default: latest]

--init <PATH>
Initialize the genesis block with the given genesis.json file.

-m, --mnemonic <MNEMONIC>
BIP39 mnemonic phrase used for generating accounts

--no-mining
Disable auto and interval mining, and mine on demand instead

--order <ORDER>
How transactions are sorted in the mempool [default: fees]

-p, --port <PORT>
Port number to listen on [default: 8545]

--steps-tracing
Enable steps tracing used for debug calls returning geth-style traces [aliases: tracing]

--ipc [<PATH>]
Starts an IPC endpoint at the given PATH argument or the default path: unix: tmp/anvil.ipc, windows: \\.\pipe\anvil.ipc

--silent
Don't print anything on startup

--timestamp <TIMESTAMP> Set the timestamp of the genesis block

-V, --version
Print version information

EVM Options

-f, --fork-url <URL>
Fetch state over a remote endpoint instead of starting from an empty state

--fork-block-number <BLOCK>
Fetch state from a specific block number over a remote endpoint (Must pass --fork-url in the same command-line)

--fork-retry-backoff <BACKOFF>
Initial retry backoff on encountering errors.

--retries <retries>
Number of retry requests for spurious networks (timed out requests). [default value= 5]

--timeout <timeout>
Timeout in ms for requests sent to remote JSON-RPC server in forking mode. [default value= 45000]

--compute-units-per-second <CUPS>
Sets the number of assumed available compute units per second for this provider [default value=330] See also, Alchemy Ratelimits

--no-rate-limit Disables rate limiting for this node's provider. Will always override --compute-units-per-second if present. [default value= false] See also, Alchemy Ratelimits

--no-storage-caching>
Explicitly disables the use of RPC caching. All storage slots are read entirely from the endpoint. This flag overrides the project's configuration file (Must pass --fork-url in the same command-line)

Executor Environment Config

--base-fee <FEE>
--block-base-fee-per-gas <FEE>
The base fee in a block

--chain-id <CHAIN_ID>
The chain ID [default: 31337]

--code-size-limit <CODE_SIZE>
EIP-170: Contract code size limit in bytes. Useful to increase this because of tests. By default, it is 0x6000 (~25kb)

--gas-limit <GAS_LIMIT>
The block gas limit

--gas-price <GAS_PRICE>
The gas price

Server Options

--allow-origin <allow-origin>
Set the CORS allow_origin [default: *]

--no-cors
Disable CORS

--host <HOST>
The IP address the server will listen on

--config-out <OUT_FILE>
Writes output of anvil as json to user-specified file

--prune-history
Don't keep full chain history

EXAMPLES

Set the number of accounts to 15 and their balance to 300 ETH

anvil --accounts 15 --balance 300

Choose the address which will execute the tests

anvil --sender 0xC8479C45EE87E0B437c09d3b8FE8ED14ccDa825E

Change how transactions are sorted in the mempool to FIFO

anvil --order fifo

Shell Completions

anvil completions shell

Generates a shell completions script for the given shell.

Supported shells are:

bash
elvish
fish
powershell
zsh

EXAMPLES

Generate shell completions script for zsh:

anvil completions zsh > $HOME/.oh-my-zsh/completions/_anvil

Usage within Docker

In order to run anvil as a service in Github Actions with the Docker container, where passing arguments to the entrypoint command is not possible, use the ANVIL_IP_ADDR environment variable to set the host's IP. ANVIL_IP_ADDR=0.0.0.0 is equivalent to providing the --host <ip> option.

chisel

NAME

chisel - Test and receive verbose feedback on Solidity inputs within a REPL environment.

SYNOPSIS

chisel [options]

Subcommands (bin)

chisel list
- Displays all cached sessions stored in ~/.foundry/cache/chisel.
chisel load <id>
- If a cached session with id = <id> exists, launches the REPL and loads the corresponding session.
chisel view <id>
- If a cached session with id = <id> exists, displays the source code of the session's REPL contract.
chisel clear-cache
- Deletes all cache files within the ~/.foundry/cache/chisel directory. These sessions are unrecoverable, so use this command with care.

Flags

See man chisel or chisel --help for all available environment configuration flags.

DESCRIPTION

Chisel is a Solidity REPL (short for "read-eval-print loop") that allows developers to write and test Solidity code snippets. It provides an interactive environment for writing and executing Solidity code, as well as a set of built-in commands for working with and debugging your code. This makes it a useful tool for quickly testing and experimenting with Solidity code without having to spin up a sandbox foundry test suite.

Usage

To open chisel, simply execute the chisel binary.

From there, input valid Solidity code. There are two kinds of inputs to the chisel prompt apart from commands:

Expressions
- Expressions are statements that return a value or otherwise can be evaluated on their own. For example, 1 << 8 is an expression that will evaluate to a uint256 with the value 256. Expressions will be evaluated up front, and will not persist in the session state past their evaluation.
- Examples:
  - address(0).balance
  - abi.encode(256, bytes32(0), "Chisel!")
  - myViewFunc(128)
  - ...
Statements
- Statements are snippets of code that are meant to persist in the session's state. Statements include variable definitions, calls to non-state-mutating functions that return a value, and contract, function, event, error, mapping, or struct definitions. If you would like an expression to be evaluated as a statement, a semi-colon (;) can be appended to the end.
- Examples:
  - uint256 a = 0xa57b
  - myStateMutatingFunc(128) || myViewFunc(128); <- Notice the ;
  - ```
  function hash64(
    bytes32 _a,
    bytes32 _b
  ) internal pure returns (bytes32 _hash) { 
      assembly {
          // Store the 64 bytes we want to hash in scratch space
          mstore(0x00, _a)
          mstore(0x20, _b)
  
          // Hash the memory in scratch space
          // and assign the result to `_hash`
          _hash := keccak256(0x00, 0x40)
      }
  }
```
- event ItHappened(bytes32 indexed hash)
- struct Complex256 { uint256 re; uint256 im; }
- ...

Available Commands

⚒️ Chisel help
=============
General
        !help | !h - Display all commands
        !quit | !q - Quit Chisel
        !exec <command> [args] | !e <command> [args] - Execute a shell command and print the output

Session
        !clear | !c - Clear current session source
        !source | !so - Display the source code of the current session
        !save [id] | !s [id] - Save the current session to cache
        !load <id> | !l <id> - Load a previous session ID from cache
        !list | !ls - List all cached sessions
        !clearcache | !cc - Clear the chisel cache of all stored sessions
        !export | !ex - Export the current session source to a script file
        !fetch <addr> <name> | !fe <addr> <name> - Fetch the interface of a verified contract on Etherscan
        !edit - Open the current session in an editor

Environment
        !fork <url> | !f <url> - Fork an RPC for the current session. Supply 0 arguments to return to a local network
        !traces | !t - Enable / disable traces for the current session

Debug
        !memdump | !md - Dump the raw memory of the current state
        !stackdump | !sd - Dump the raw stack of the current state
        !rawstack <var> | !rs <var> - Display the raw value of a variable's stack allocation. For variables that are > 32 bytes in length, this will display their memory pointer.

General

!help | !h

Display all commands.

!quit | !q

Quit Chisel.

!exec <command> [args] | !e <command> [args]

Execute a shell command and print the output.

Example:

➜ !e ls
CHANGELOG.md
LICENSE
README.md
TESTS.md
artifacts
cache
contracts
crytic-export
deploy
deploy-config
deployments
dist
echidna.yaml
forge-artifacts
foundry.toml
hardhat.config.ts
layout-lock.json
node_modules
package.json
scripts
slither.config.json
slither.db.json
src
tasks
test-case-generator
tsconfig.build.json
tsconfig.build.tsbuildinfo
tsconfig.json

Session

!clear | !c

Clear current session source.

Under the hood, each Chisel session has an underlying contract that is altered as you input statements. This command clears this contract and resets your session to the default state.

!source | !so

Display the source code of the current session.

As mentioned above, each Chisel session has an underlying contract. This command will display the source code of this contract.

!save [id] | !s [id]

Save the current session to cache.

Chisel allows for caching sessions, which can be very useful if you are testing more complex logic in Chisel or if you want to return to a session at a later time. All cached Chisel sessions are stored in ~/.foundry/cache/chisel.

If an id argument is not supplied, Chisel will automatically assign a numerical ID to the session you are saving.

!load <id> | !l <id>

Load a previous session ID from cache.

This command will load a previously cached session from the cache. Along with the session's source, all environment settings will also be loaded. The id argument must correspond with an existing cached session in the ~/.foundry/cache/chisel directory.

!list | !ls

List all cached sessions.

This command will display all cached chisel sessions within the ~/.foundry/cache/chisel directory.

!clearcache | !cc

Clear the chisel cache of all stored sessions.

Deletes all cache files within the ~/.foundry/cache/chisel directory. These sessions are unrecoverable, so use this command with care.

!export | !ex

Export the current session source to a script file.

If chisel was executed from the root directory of a foundry project, it is possible to export your current session to a foundry script in the scripts dir of your project.

!fetch <addr> <name> | !fe <addr> <name>

Fetch the interface of a verified contract on Etherscan.

This command will attempt to parse the interface of a verified contract @ <addr> from the Etherscan API. If successful, the interface will be inserted into the session source with the name <name>.

At the moment, only interfaces of verified contracts on Ethereum mainnet can be fetched. In the future, Chisel will support fetching interfaces from multiple Etherscan-supported chains.

!edit

Open the current session's run() function in an editor.

chisel will use the editor defined in the $EDITOR environment variable.

Environment

!fork <url> | !f <url>

Fork an RPC for the current session. Supply 0 arguments to return to a local network.

Attempts to fork the state of the provided RPC. If no URL is provided, returns to using a blank, local devnet state.

!traces | !t

Enable / disable traces for the current session.

When tracing is enabled, foundry-style call tracing and logs will be printed after each statement is inserted.

Debug

!memdump | !md

Dump the raw memory of the current state.

Attempts to dump the raw memory of the machine state after the last instruction of the REPL contract's run function has finished executing.

!stackdump | !sd

Dump the raw stack of the current state.

Attempts to dump the raw stack of the machine state after the last instruction of the REPL contract's run function has finished executing.

!rawstack <var> | !rs <var>

Display the raw value of a variable's stack allocation. For variables that are > 32 bytes in length, this will display their memory pointer.

This command is useful when you want to view the full raw stack allocation for a variable that is less than 32 bytes in length.

Example:

➜ address addr
➜ assembly {
    addr := not(0)
}
➜ addr
Type: address
└ Data: 0xffffffffffffffffffffffffffffffffffffffff
➜ !rs addr
Type: bytes32
└ Data: 0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
➜

Config Reference

Config Overview

Foundry's configuration system allows you to configure its tools.

Profiles

Configuration can be arbitrarily namespaced into profiles. The default profile is named default, and all other profiles inherit values from this profile. Profiles are defined in the profile map.

To add a profile named local, you would add:

[profile.local]

You can select the profile to use by setting the FOUNDRY_PROFILE environment variable.

Global configuration

You can create a foundry.toml file in ~/.foundry folder to configure Foundry globally.

Environment variables

Configuration can be overriden with FOUNDRY_ and DAPP_ prefixed environment variables.

Exceptions are:

FOUNDRY_FFI, DAPP_FFI

Configuration format

Configuration files are written in the TOML format, with simple key-value pairs inside of sections.

This page describes each configuration key in detail. To see the default values, either refer to the specific key in this document, or see the default config.

Configuration keys

This section documents all configuration keys. All configuration keys must live under a profile, such as default.

Project

Configuration related to the project in general.

`src`

Type: string
Default: src
Environment: FOUNDRY_SRC or DAPP_SRC

The path to the contract sources relative to the root of the project.

`test`

Type: string
Default: test
Environment: FOUNDRY_TEST or DAPP_TEST

The path to the test contract sources relative to the root of the project.

`out`

Type: string
Default: out
Environment: FOUNDRY_OUT or DAPP_OUT

The path to put contract artifacts in, relative to the root of the project.

`libs`

Type: array of strings (paths)
Default: lib
Environment: FOUNDRY_LIBS or DAPP_LIBS

An array of paths that contain libraries, relative to the root of the project.

`cache`

Type: boolean
Default: true
Environment: FOUNDRY_CACHE or DAPP_CACHE

Whether or not to enable caching. If enabled, the result of compiling sources, tests, and dependencies, are cached in cache.

`cache_path`

Type: string
Default: cache
Environment: FOUNDRY_CACHE_PATH or DAPP_CACHE_PATH

The path to the cache, relative to the root of the project.

`broadcast`

Type: string
Default: broadcast

The path to the broadcast transaction logs, relative to the root of the project.

`force`

Type: boolean
Default: false
Environment: FOUNDRY_FORCE or DAPP_FORCE

Whether or not to perform a clean build, discarding the cache.

Solidity compiler

Configuration related to the behavior of the Solidity compiler.

Sections

General

Configuration related to the behavior of the Solidity compiler.

`remappings`

Type: array of strings (remappings)
Default: none
Environment: FOUNDRY_REMAPPINGS or DAPP_REMAPPINGS

An array of remappings in the following format: <name>=<target>.

A remapping remaps Solidity imports to different directories. For example, the following remapping

@openzeppelin/=node_modules/@openzeppelin/openzeppelin-contracts/

with an import like

import "@openzeppelin/contracts/utils/Context.sol";

becomes

import "node_modules/@openzeppelin/openzeppelin-contracts/contracts/utils/Context.sol";

`auto_detect_remappings`

Type: boolean
Default: true
Environment: FOUNDRY_AUTO_DETECT_REMAPPINGS or DAPP_AUTO_DETECT_REMAPPINGS

If enabled, Foundry will automatically try auto-detect remappings by scanning the libs folder(s).

If set to false, only the remappings in foundry.toml and remappings.txt are used.

`allow_paths`

Type: array of strings (paths)
Default: none
Environment: FOUNDRY_ALLOW_PATHS or DAPP_ALLOW_PATHS

Tells solc to allow reading source files from additional directories. This is mainly relevant for complex workspaces managed by pnmp or similar.

`include_paths`

Type: array of strings (paths)
Default: none
Environment: FOUNDRY_INCLUDE_PATHS or DAPP_INCLUDE_PATHS

Make an additional source directory available to the default import callback. Use this option if you want to import contracts whose location is not fixed in relation to your main source tree, e.g. third-party libraries installed using a package manager. Can be used multiple times. Can only be used if base path has a non-empty value.

`libraries`

Type: array of strings (libraries)
Default: none
Environment: FOUNDRY_LIBRARIES or DAPP_LIBRARIES

An array of libraries to link against in the following format: <file>:<lib>:<address>, for example: src/MyLibrary.sol:MyLibrary:0xfD88CeE74f7D78697775aBDAE53f9Da1559728E4.

`solc_version`

Type: string (semver)
Default: none
Environment: FOUNDRY_SOLC_VERSION or DAPP_SOLC_VERSION

If specified, overrides the auto-detection system (more below) and uses a single Solidity compiler version for the project.

Only strict versions are supported (i.e. 0.8.11 is valid, but ^0.8.0 is not).

`auto_detect_solc`

Type: boolean
Default: true
Environment: FOUNDRY_AUTO_DETECT_SOLC or DAPP_AUTO_DETECT_SOLC

If enabled, Foundry will automatically try to resolve appropriate Solidity compiler versions to compile your project.

This key is ignored if solc_version is set.

`offline`

Type: boolean
Default: false
Environment: FOUNDRY_OFFLINE or DAPP_OFFLINE

If enabled, Foundry will not attempt to download any missing solc versions.

If both offline and auto-detect-solc are set to true, the required version(s) of solc will be auto detected but any missing versions will not be installed.

`ignored_error_codes`

Type: array of integers/strings
Default: none for source, SPDX license identifiers and contract size for tests
Environment: FOUNDRY_IGNORED_ERROR_CODES or DAPP_IGNORED_ERROR_CODES

An array of Solidity compiler error codes to ignore during build, such as warnings.

Valid values are:

license: 1878
code-size: 5574
func-mutability: 2018
unused-var: 2072
unused-param: 5667
unused-return: 9302
virtual-interfaces: 5815
missing-receive-ether: 3628
shadowing: 2519
same-varname: 8760
unnamed-return: 6321
unreachable: 5740
pragma-solidity: 3420

`deny_warnings`

Type: boolean
Default: false
Environment: FOUNDRY_DENY_WARNINGS or DAPP_DENY_WARNINGS

If enabled, Foundry will treat Solidity compiler warnings as errors, stopping artifacts from being written to disk.

`evm_version`

Type: string
Default: london
Environment: FOUNDRY_EVM_VERSION or DAPP_EVM_VERSION

The EVM version to use during tests. The value must be an EVM hardfork name, such as london, byzantium, etc.

`revert_strings`

Type: string
Default: default
Environment: FOUNDRY_REVERT_STRINGS or DAPP_REVERT_STRINGS

Possible values are:

default does not inject compiler-generated revert strings and keeps user-supplied ones.
strip removes all revert strings (if possible, i.e. if literals are used) keeping side-effects.
debug injects strings for compiler-generated internal reverts, implemented for ABI encoders V1 and V2 for now.
verboseDebug even appends further information to user-supplied revert strings (not yet implemented).

`extra_output_files`

Type: array of strings
Default: none
Environment: N/A

Extra output from the Solidity compiler that should be written to files in the artifacts directory.

Valid values are:

metadata: Written as a metadata.json file in the artifacts directory
ir: Written as a .ir file in the artifacts directory
irOptimized: Written as a .iropt file in the artifacts directory
ewasm: Written as a .ewasm file in the artifacts directory
evm.assembly: Written as a .asm file in the artifacts directory

`extra_output`

Type: array of strings
Default: see below
Environment: N/A

Extra output to include in the contract's artifact.

The following values are always set, since they're required by Forge:

extra_output = [
  "abi",
  "evm.bytecode",
  "evm.deployedBytecode",
  "evm.methodIdentifiers",
]

For a list of valid values, see the [Solidity docs][output-desc].

`bytecode_hash`

Type: string
Default: ipfs
Environment: FOUNDRY_BYTECODE_HASH or DAPP_BYTECODE_HASH

Determines the hash method for the metadata hash that is appended to the bytecode.

Valid values are:

ipfs (default)
bzzr1
none

`sparse_mode`

Type: boolean
Default: false
Environment: FOUNDRY_SPARSE_MODE or DAPP_SPARSE_MODE

Enables sparse mode for builds.

Optimizer

Configuration related to the Solidity optimizer.

`optimizer`

Type: boolean
Default: true
Environment: FOUNDRY_OPTIMIZER or DAPP_OPTIMIZER

Whether or not to enable the Solidity optimizer.

`optimizer_runs`

Type: integer
Default: 200
Environment: FOUNDRY_OPTIMIZER_RUNS or DAPP_OPTIMIZER_RUNS

The amount of optimizer runs to perform.

`via_ir`

Type: boolean
Default: false
Environment: FOUNDRY_VIA_IR or DAPP_VIA_IR

If set to true, changes compilation pipeline to go through the new IR optimizer.

`[optimizer_details]`

The optimizer details section is used to tweak how the Solidity optimizer behaves. There are several configurable values in this section (each of them are booleans):

peephole
inliner
jumpdest_remover
order_literals
deduplicate
cse
constant_optimizer
yul

Refer to the Solidity compiler input description for the default values.

`[optimizer_details.yul_details]`

The Yul details subsection of the optimizer details section is used to tweak how the new IR optimizer behaves. There are two configuration values:

stack_allocation: Tries to improve the allocation of stack slots by freeing them up earlier.
optimizer_steps: Selects the optimizer steps to be applied.

Refer to the Solidity compiler input description for the default values.

ℹ️ Note
If you encounter compiler errors when using via_ir, explicitly enable the legacy optimizer and leave optimizer_steps as an empty string

Model checker

The Solidity model checker is a built-in opt-in module that is available in Solidity compilers for OSX and Linux. Learn more about the model checker in the Solidity compiler documentation

ℹ️ Note
The model checker requires z3 version 4.8.8 or 4.8.14 on Linux.

The model checker settings are configured in the [model_checker] section of the configuration.

The model checker will run when forge build is invoked, and any findings will show up as warnings.

These are the recommended settings when using the model checker:

[profile.default.model_checker]
contracts = {'/path/to/project/src/Contract.sol' = ['Contract']}
engine = 'chc'
timeout = 10000
targets = ['assert']

Setting which contract should be verified is extremely important, otherwise all available contracts will be verified which may take a long time.

The recommended engine is chc, but bmc and all (which runs both) are also accepted.

It is also important to set a proper timeout (given in milliseconds), since the default time given to the underlying solver may not be enough.

If no verification targets are given, only assertions will be checked.

`[model_checker]`

The following keys are available in the model checker section.

`model_checker.contracts`

Type: table
Default: all
Environment: N/A

Specifies what contracts the model checker will analyze.

The key of the table is the path to a source file, and the value is an array of contract names to check.

For example:

[profile.default.model_checker]
contracts = { "src/MyContracts.sol" = ["ContractA", "ContractB"] }

`model_checker.div_mod_with_slacks`

Type: boolean
Default: false
Environment: N/A

Sets how division and modulo operations should be encoded.

Refer to the Solidity documentation for more information.

`model_checker.engine`

Type: string (see below)
Default: all
Environment: N/A

Specifies the model checker engine to run. Valid values are:

chc: The constrained horn clauses engine
bmc: The bounded model checker engine
all: Runs both engines

Refer to the Solidity documentation for more information on the engines.

`model_checker.invariants`

Type: array of strings
Default: N/A
Environment: N/A

Sets the model checker invariants. Valid values are:

contract: Contract Invariants
reentrancy: Reentrancy Properties

Refer to the Solidity documentation for more information on the invariants.

`model_checker.show_unproved`

Type: boolean
Default: false
Environment: N/A

Whether or not to output all unproved targets.

Refer to the Solidity documentation for more information.

`model_checker.solvers`

Type: array of strings
Default: N/A
Environment: N/A

Sets the model checker solvers. Valid values are:

cvc4
eld: introduced in v0.8.18
smtlib2
z3

Refer to the Solidity documentation for more information.

`model_checker.timeout`

Type: number (milliseconds)
Default: N/A
Environment: N/A

Sets the timeout for the underlying model checker engines (in milliseconds).

`model_checker.targets`

Type: array of strings
Default: assert
Environment: N/A

Sets the model checker targets. Valid values are:

assert: Assertions
underflow: Arithmetic underflow
overflow: Arithmetic overflow
divByZero: Division by zero
constantCondition: Trivial conditions and unreachable code
popEmptyArray: Popping an empty array
outOfBounds: Out of bounds array/fixed bytes index access
default: All of the above (note: not the default for Forge)

Testing

Configuration related to the behavior of forge test.

Sections

General

`verbosity`

Type: integer
Default: 0
Environment: FOUNDRY_VERBOSITY or DAPP_VERBOSITY

The verbosity level to use during tests.

Level 2 (-vv): Logs emitted during tests are also displayed.
Level 3 (-vvv): Stack traces for failing tests are also displayed.
Level 4 (-vvvv): Stack traces for all tests are displayed, and setup traces for failing tests are displayed.
Level 5 (-vvvvv): Stack traces and setup traces are always displayed.

`ffi`

Type: boolean
Default: false
Environment: FOUNDRY_FFI or DAPP_FFI

Whether or not to enable the ffi cheatcode.

Warning: Enabling this cheatcode has security implications for your project, as it allows tests to execute arbitrary programs on your computer.

`sender`

Type: string (address)
Default: 0x1804c8AB1F12E6bbf3894d4083f33e07309d1f38
Environment: FOUNDRY_SENDER or DAPP_SENDER

The value of msg.sender in tests.

`tx_origin`

Type: string (address)
Default: 0x1804c8AB1F12E6bbf3894d4083f33e07309d1f38
Environment: FOUNDRY_TX_ORIGIN or DAPP_TX_ORIGIN

The value of tx.origin in tests.

`initial_balance`

Type: string (hexadecimal)
Default: 0xffffffffffffffffffffffff
Environment: FOUNDRY_INITIAL_BALANCE or DAPP_INITIAL_BALANCE

The initial balance of the test contracts in wei, written in hexadecimal.

`block_number`

Type: integer
Default: 1
Environment: FOUNDRY_BLOCK_NUMBER or DAPP_BLOCK_NUMBER

The value of block.number in tests.

`chain_id`

Type: integer
Default: 31337
Environment: FOUNDRY_CHAIN_ID or DAPP_CHAIN_ID

The value of the chainid opcode in tests.

`gas_limit`

Type: integer or string
Default: 9223372036854775807
Environment: FOUNDRY_GAS_LIMIT or DAPP_GAS_LIMIT

The gas limit for each test case.

ℹ️ Note

Due to a limitation in a dependency of Forge, you cannot raise the gas limit beyond the default without changing the value to a string.

In order to use higher gas limits use a string:

gas_limit = "18446744073709551615" # u64::MAX

`gas_price`

Type: integer
Default: 0
Environment: FOUNDRY_GAS_PRICE or DAPP_GAS_PRICE

The price of gas (in wei) in tests.

`block_base_fee_per_gas`

Type: integer
Default: 0
Environment: FOUNDRY_BLOCK_BASE_FEE_PER_GAS or DAPP_BLOCK_BASE_FEE_PER_GAS

The base fee per gas (in wei) in tests.

`block_coinbase`

Type: string (address)
Default: 0x0000000000000000000000000000000000000000
Environment: FOUNDRY_BLOCK_COINBASE or DAPP_BLOCK_COINBASE

The value of block.coinbase in tests.

`block_timestamp`

Type: integer
Default: 1
Environment: FOUNDRY_BLOCK_TIMESTAMP or DAPP_BLOCK_TIMESTAMP

The value of block.timestamp in tests.

`block_difficulty`

Type: integer
Default: 0
Environment: FOUNDRY_BLOCK_DIFFICULTY or DAPP_BLOCK_DIFFICULTY

The value of block.difficulty in tests.

`gas_reports`

Type: array of strings (contract names)
Default: ["*"]
Environment: FOUNDRY_GAS_REPORTS or DAPP_GAS_REPORTS

The contracts to print gas reports for.

`no_storage_caching`

Type: boolean
Default: false
Environment: FOUNDRY_NO_STORAGE_CACHING or DAPP_NO_STORAGE_CACHING

If set to true, then block data from RPC endpoints in tests will not be cached. Otherwise, the data is cached to $HOME/.foundry/cache/<chain id>/<block number>.

`[rpc_storage_caching]`

The [rpc_storage_caching] block determines what RPC endpoints are cached.

`rpc_storage_caching.chains`

Type: string or array of strings (chain names)
Default: all
Environment: N/A

Determines what chains are cached. By default, all chains are cached.

Valid values are:

"all"
A list of chain names, e.g. ["optimism", "mainnet"]

`rpc_storage_caching.endpoints`

Type: string or array of regex patterns (to match URLs)
Default: remote
Environment: N/A

Determines what RPC endpoints are cached. By default, only remote endpoints are cached.

Valid values are:

all
remote (default)
A list of regex patterns, e.g. ["localhost"]

`eth_rpc_url`

Type: string
Default: none
Environment: FOUNDRY_ETH_RPC_URL or DAPP_ETH_RPC_URL

The url of the rpc server that should be used for any rpc calls.

`etherscan_api_key`

Type: string
Default: none
Environment: FOUNDRY_ETHERSCAN_API_KEY or DAPP_ETHERSCAN_API_KEY

The etherscan API key for RPC calls.

`match-test`

Type: regex
Default: none
Environment: FOUNDRY_MATCH_TEST or DAPP_MATCH_TEST

Only run test methods matching regex. Equivalent to forge test --match-test <TEST_PATTERN>

`no-match-test`

Type: regex
Default: none
Environment: FOUNDRY_NO_MATCH_TEST or DAPP_NO_MATCH_TEST

Only run test methods not matching regex. Equivalent to forge test --no-match-test <TEST_PATTERN_INVERSE>

`match-contract`

Type: regex
Default: none
Environment: FOUNDRY_MATCH_CONTRACT or DAPP_MATCH_CONTRACT

Only run test methods in contracts matching regex. Equivalent to forge test --match-contract <CONTRACT_PATTERN>

`no-match-contract`

Type: regex
Default: none
Environment: FOUNDRY_NO_MATCH_CONTRACT or DAPP_NO_MATCH_CONTRACT

Only run test methods in contracts not matching regex. Equivalent to forge test --no-match-contract <CONTRACT_PATTERN_INVERSE>

`match-path`

Type: regex
Default: none
Environment: FOUNDRY_MATCH_PATH or DAPP_MATCH_PATH

Only runs test methods on files matching the path. Equivalent to forge test --match-path <PATH_PATTERN>

`no-match-path`

Type: regex
Default: none
Environment: FOUNDRY_NO_MATCH_PATH or DAPP_NO_MATCH_PATH

Only runs test methods on files not matching the path. Equivalent to forge test --no-match-path <PATH_PATTERN_INVERSE>

`block_gas_limit`

Type: integer
Default: none
Environment: FOUNDRY_BLOCK_GAS_LIMIT or DAPP_BLOCK_GAS_LIMIT

The block.gaslimit value during EVM execution.

`memory_limit`

Type: integer
Default: 33554432
Environment: FOUNDRY_MEMORY_LIMIT or DAPP_MEMORY_LIMIT

The memory limit of the EVM in bytes.

`names`

Type: boolean
Default: false
Environment: FOUNDRY_NAMES or DAPP_NAMES

Print compiled contract names.

`sizes`

Type: boolean
Default: false
Environment: FOUNDRY_SIZES or DAPP_SIZES

Print compiled contract sizes.

`rpc_endpoints`

Type: table of RPC endpoints
Default: none
Environment: none

This section lives outside of profiles and defines a table of RPC endpoints, where the key specifies the RPC endpoints's name and the value is the RPC endpoint itself.

The value can either be a valid RPC endpoint or a reference to an environment variable (wrapped with in ${}).

These RPC endpoints can be used in tests and Solidity scripts (see vm.rpc).

The following example defines an endpoint named optimism and an endpoint named mainnet that references an environment variable RPC_MAINNET:

[rpc_endpoints]
optimism = "https://optimism.alchemyapi.io/v2/..."
mainnet = "${RPC_MAINNET}"

Fuzz

Configuration values for [fuzz] section.

`runs`

Type: integer
Default: 256
Environment: FOUNDRY_FUZZ_RUNS or DAPP_FUZZ_RUNS

The amount of fuzz runs to perform for each fuzz test case. Higher values gives more confidence in results at the cost of testing speed.

`max_test_rejects`

Type: integer
Default: 65536
Environment: FOUNDRY_FUZZ_MAX_TEST_REJECTS

The maximum number of combined inputs that may be rejected before the test as a whole aborts. "Global" filters apply to the whole test case. If the test case is rejected, the whole thing is regenerated.

`seed`

Type: string (hexadecimal)
Default: none
Environment: FOUNDRY_FUZZ_SEED

Optional seed for the fuzzing RNG algorithm.

`dictionary_weight`

Type: integer (between 0 and 100)
Default: 40
Environment: FOUNDRY_FUZZ_DICTIONARY_WEIGHT

The weight of the dictionary.

`include_storage`

Type: boolean
Default: true
Environment: FOUNDRY_FUZZ_INCLUDE_STORAGE

The flag indicating whether to include values from storage.

`include_push_bytes`

Type: boolean
Default: true
Environment: FOUNDRY_FUZZ_INCLUDE_PUSH_BYTES

The flag indicating whether to include push bytes values.

Invariant

Configuration values for [invariant] section.

ℹ️ Note

Configuration for [invariant] section has the fallback logic for common config entries (runs, seed, dictionary_weight etc).

If the entries are not set in either section, then the defaults will be used.

If the entries are set in the [fuzz] section, but are not set in the [invariant] section, these values will automatically be set to the values specified in the [fuzz] section.

For any profile other than default:

If at least one entry is set in the [invariant] (same as [profile.default.invariant]) section, then the values from [invariant] section will be used, including defaults.

If no entry is set in the [invariant] section, but there are entries in the [fuzz] (same as [profile.default.fuzz]) section, then the values from the [fuzz] section will be used.

If it's none of the cases described above, then the defaults will be used.

`runs`

Type: integer
Default: 256
Environment: FOUNDRY_INVARIANT_RUNS

The number of runs that must execute for each invariant test group. See also fuzz.runs

`depth`

Type: integer
Default: 15
Environment: FOUNDRY_INVARIANT_DEPTH

The number of calls executed to attempt to break invariants in one run.

`fail_on_revert`

Type: boolean
Default: false
Environment: FOUNDRY_INVARIANT_FAIL_ON_REVERT

Fails the invariant fuzzing if a revert occurs.

`call_override`

Type: boolean
Default: false
Environment: FOUNDRY_INVARIANT_CALL_OVERRIDE

Overrides unsafe external calls when running invariant tests, useful for e.g. performing reentrancy checks.

`dictionary_weight`

Type: integer (between 0 and 100)
Default: 80
Environment: FOUNDRY_INVARIANT_DICTIONARY_WEIGHT

The weight of the dictionary. See also fuzz.dictionary_weight

`include_storage`

Type: boolean
Default: true
Environment: FOUNDRY_FUZZ_INCLUDE_STORAGE

The flag indicating whether to include values from storage. See also fuzz.include_storage

`include_push_bytes`

Type: boolean
Default: true
Environment: FOUNDRY_FUZZ_INCLUDE_PUSH_BYTES

The flag indicating whether to include push bytes values. See also fuzz.include_push_bytes

In-line test configuration

Foundry users are enabled to specify overall test configurations, using a combination of ENV variables and config statements in the foundry.toml. Checkout the Testing reference for a detailed description.

Despite this may work in the general case, some tests may need finer control over their configuration. For such reason Forge provides a way to specify per-test configs for invariant and fuzz testing scenarios.

Users can in-line test config statements directly in Solidity comments. This would affect the behavior of the forge test command for a specific test instance, as illustrated in the example below.

contract MyTest is Test {
  /// forge-config: default.fuzz.runs = 100
  /// forge-config: ci.fuzz.runs = 500
  function test_SimpleFuzzTest(uint256 x) public {
    // --- snip ---
  }
}

What we are asking here is to run our fuzzer 100 and 500 times for the default and ci profiles respectively. The interesting fact is that this would override any fuzz runs setup existing at a global level. All other configs would be inherited from the global context, making this acting as a fallback for all possible configurations.

Block comments

In-line test configurations can also be expressed in block comments, as illustrated in the example.

contract MyTest is Test {
  /**
   * forge-config: default.fuzz.runs = 1024
   * forge-config: default.fuzz.max-test-rejects = 500
   */
  function test_SimpleFuzzTest(uint256 x) public {
    // --- snip ---
  }
}

In-line fuzz configs

Users can specify the configs described in the table. Each statement must have a prefix of the form forge-config: ${PROFILE}.fuzz.

Parameter	Type	Description
`runs`	integer	The amount of fuzz runs to perform for this specific test case. `Reference`.
`max-test-rejects`	integer	The maximum number of combined inputs that may be rejected before the test as a whole aborts. `Reference`.

Fuzz config example

contract MyFuzzTest is Test {
  /// forge-config: default.fuzz.runs = 100
  /// forge-config: default.fuzz.max-test-rejects = 2
  function test_InlineConfig(uint256 x) public {
    // --- snip ---
  }
}

In-line invariant configs

Users can specify the configs described in the table. Each statement must have a prefix of the form forge-config: ${PROFILE}.invariant.

Parameter	Type	Description
`runs`	integer	The amount of invariant runs to perform for this specific test case. `Reference`.
`depth`	integer	The number of calls executed to attempt to break invariant in one run. `Reference`.
`fail-on-revert`	boolean	Fails the invariant fuzzing if a revert occurs. `Reference`.
`call-override`	boolean	Overrides unsafe external calls when running invariant test. `Reference`.

Invariant config example

contract MyInvariantTest is Test {
  /// forge-config: default.invariant.runs = 100
  /// forge-config: default.invariant.depth = 2
  /// forge-config: default.invariant.fail-on-revert = false
  /// forge-config: default.invariant.call-override = true
  function invariant_InlineConfig() public {
    // --- snip ---
  }
}

Formatter

Configuration related to the behavior of the Forge formatter. Each of these keys live under the [fmt] section.

`line_length`

Type: number
Default: 120
Environment: FOUNDRY_FMT_LINE_LENGTH or DAPP_FMT_LINE_LENGTH

Maximum line length where formatter will try to wrap the line.

`tab_width`

Type: number
Default: 4
Environment: FOUNDRY_FMT_TAB_WIDTH or DAPP_FMT_TAB_WIDTH

Number of spaces per indentation level.

`bracket_spacing`

Type: bool
Default: false
Environment: FOUNDRY_FMT_BRACKET_SPACING or DAPP_FMT_BRACKET_SPACING

Whether or not to print spaces between brackets.

`int_types`

Type: string
Default: long
Environment: FOUNDRY_FMT_INT_TYPES or DAPP_FMT_INT_TYPES

Style of uint/int256 types. Valid values are:

long (default): Use the explicit uint256 or int256
short: Use the implicit uint or int
preserve: Use the type defined in the source code

`multiline_func_header`

Type: string
Default: attributes_first
Environment: FOUNDRY_FMT_MULTILINE_FUNC_HEADER or DAPP_FMT_MULTILINE_FUNC_HEADER

Style of multiline function header in case it doesn't fit in one line. Valid values are:

attributes_first (default): Write function attributes multiline first
params_first: Write function parameters multiline first
all: If function parameters or attributes are multiline, multiline everything

`quote_style`

Type: string
Default: double
Environment: FOUNDRY_FMT_QUOTE_STYLE or DAPP_FMT_QUOTE_STYLE

Defines the quotation mark style. Valid values are:

double (default): Use double quotes where possible (")
single: Use single quotes where possible (')
preserve: Use quotation mark defined in the source code

`number_underscore`

Type: string
Default: preserve
Environment: FOUNDRY_FMT_NUMBER_UNDERSCORE or DAPP_FMT_NUMBER_UNDERSCORE

Style of underscores in number literals. Valid values are:

preserve (default): Use the underscores defined in the source code
thousands: Add an underscore every thousand, if greater than 9999. i.e. 1000 is formatted as 1000 and 10000 as 10_000
remove: Remove all underscores

`override_spacing`

Type: bool
Default: true
Environment: FOUNDRY_FMT_OVERRIDE_SPACING or DAPP_FMT_OVERRIDE_SPACING

Whether or not to print a space in override attributes for contract state variables, functions, and modifiers.

`wrap_comments`

Type: bool
Default: false
Environment: FOUNDRY_FMT_WRAP_COMMENTS or DAPP_FMT_WRAP_COMMENTS

Whether or not to wrap comments on line_length reached.

`ignore`

Type: array of strings (patterns)
Default: []
Environment: FOUNDRY_FMT_IGNORE or DAPP_FMT_IGNORE

List of files to ignore when formatting. This is a comma separated list of glob patterns.

Documentation Generator

Configuration related to the behavior of the Forge documentation generator. These keys are set in [doc] section.

`out`

Type: string
Default: docs
Environment: FOUNDRY_DOC_OUT

An output path for generated documentation.

`title`

Type: string
Environment: FOUNDRY_DOC_TITLE

Title for the generated documentation.

`book`

Type: string
Default: ./book.toml
Environment: FOUNDRY_DOC_BOOK

Path to user provided book.toml. It will be merged with default settings during doc generation.

`repository`

Type: string
Environment: FOUNDRY_DOC_REPOSITORY

The git repository URL. Used to provide links to git source files. If missing, forge will attempt to look up the current origin url and use its value.

`ignore`

Type: array of strings (patterns)
Default: []
Environment: FOUNDRY_DOC_IGNORE

List of files to ignore when generating documentation. This is a comma separated list of glob patterns.

Etherscan

Configuration related to Etherscan, such as API keys. This configuration is used in various places by Forge.

The [etherscan] section is a mapping of keys to Etherscan configuration tables. The Etherscan configuration tables hold the following keys:

key (string) (required): The Etherscan API key for the given network. The value of this property can also point to an environment variable.
chain: The chain name or ID of the chain this Etherscan configuration is for.
url: The Etherscan API URL.

If the key of the configuration is a chain name, then chain is not required, otherwise it is. url can be used to explicitly set the Etherscan API URL for chains not natively supported by name.

Using TOML inline table syntax, all of these are valid:

[etherscan]
mainnet = { key = "${ETHERSCAN_MAINNET_KEY}" }
mainnet2 = { key = "ABCDEFG", chain = "mainnet" }
optimism = { key = "1234567" }
unknown_chain = { key = "ABCDEFG", url = "<etherscan api url for this chain>" }

Cheatcodes Reference

Cheatcodes give you powerful assertions, the ability to alter the state of the EVM, mock data, and more.

Cheatcodes are made available through use of the cheatcode address (0x7109709ECfa91a80626fF3989D68f67F5b1DD12D).

ℹ️ Note

If you encounter errors for this address when using fuzzed addresses in your tests, you may wish to exclude it from your fuzz tests by using the following line:
vm.assume(address_ != 0x7109709ECfa91a80626fF3989D68f67F5b1DD12D);

You can also access cheatcodes easily via vm available in Forge Standard Library's Test contract.

Forge Standard Library Cheatcodes

Forge Std implements wrappers around cheatcodes, which combine multiple standard cheatcodes to improve development experience. These are not technically cheatcodes, but rather compositions of Forge's cheatcodes.

You can view the list of Forge Standard Library's cheatcode wrappers in the references section. You can reference the Forge Std source code to learn more about how the wrappers work under the hood.

Cheatcode Types

Below are some subsections for the different Forge cheatcodes.

Environment: Cheatcodes that alter the state of the EVM.
Assertions: Cheatcodes that are powerful assertions
Fuzzer: Cheatcodes that configure the fuzzer
External: Cheatcodes that interact with external state (files, commands, ...)
Utilities: Smaller utility cheatcodes
Forking: Forking mode cheatcodes
Snapshots: Snapshot cheatcodes
RPC: RPC related cheatcodes
File: Cheatcodes for working with files

Add a new cheatcode

If you need a new feature, consider contributing to the Foundry's codebase to add the cheatcode.

Cheatcodes Interface

This is a Solidity interface for all of the cheatcodes present in Forge.

interface CheatCodes {
    // This allows us to getRecordedLogs()
    struct Log {
        bytes32[] topics;
        bytes data;
    }

    // Possible caller modes for readCallers()
    enum CallerMode {
        None,
        Broadcast,
        RecurrentBroadcast,
        Prank,
        RecurrentPrank
    }

    // Set block.timestamp
    function warp(uint256) external;

    // Set block.number
    function roll(uint256) external;

    // Set block.basefee
    function fee(uint256) external;

    // Set block.difficulty
    // Does not work from the Paris hard fork and onwards, and will revert instead.
    function difficulty(uint256) external;
    
    // Set block.prevrandao
    // Does not work before the Paris hard fork, and will revert instead.
    function prevrandao(bytes32) external;

    // Set block.chainid
    function chainId(uint256) external;

    // Loads a storage slot from an address
    function load(address account, bytes32 slot) external returns (bytes32);

    // Stores a value to an address' storage slot
    function store(address account, bytes32 slot, bytes32 value) external;

    // Signs data
    function sign(uint256 privateKey, bytes32 digest)
        external
        returns (uint8 v, bytes32 r, bytes32 s);

    // Computes address for a given private key
    function addr(uint256 privateKey) external returns (address);

    // Derive a private key from a provided mnemonic string,
    // or mnemonic file path, at the derivation path m/44'/60'/0'/0/{index}.
    function deriveKey(string calldata, uint32) external returns (uint256);
    // Derive a private key from a provided mnemonic string, or mnemonic file path,
    // at the derivation path {path}{index}
    function deriveKey(string calldata, string calldata, uint32) external returns (uint256);

    // Gets the nonce of an account
    function getNonce(address account) external returns (uint64);

    // Sets the nonce of an account
    // The new nonce must be higher than the current nonce of the account
    function setNonce(address account, uint64 nonce) external;

    // Performs a foreign function call via terminal
    function ffi(string[] calldata) external returns (bytes memory);

    // Set environment variables, (name, value)
    function setEnv(string calldata, string calldata) external;

    // Read environment variables, (name) => (value)
    function envBool(string calldata) external returns (bool);
    function envUint(string calldata) external returns (uint256);
    function envInt(string calldata) external returns (int256);
    function envAddress(string calldata) external returns (address);
    function envBytes32(string calldata) external returns (bytes32);
    function envString(string calldata) external returns (string memory);
    function envBytes(string calldata) external returns (bytes memory);

    // Read environment variables as arrays, (name, delim) => (value[])
    function envBool(string calldata, string calldata)
        external
        returns (bool[] memory);
    function envUint(string calldata, string calldata)
        external
        returns (uint256[] memory);
    function envInt(string calldata, string calldata)
        external
        returns (int256[] memory);
    function envAddress(string calldata, string calldata)
        external
        returns (address[] memory);
    function envBytes32(string calldata, string calldata)
        external
        returns (bytes32[] memory);
    function envString(string calldata, string calldata)
        external
        returns (string[] memory);
    function envBytes(string calldata, string calldata)
        external
        returns (bytes[] memory);

    // Read environment variables with default value, (name, value) => (value)
    function envOr(string calldata, bool) external returns (bool);
    function envOr(string calldata, uint256) external returns (uint256);
    function envOr(string calldata, int256) external returns (int256);
    function envOr(string calldata, address) external returns (address);
    function envOr(string calldata, bytes32) external returns (bytes32);
    function envOr(string calldata, string calldata) external returns (string memory);
    function envOr(string calldata, bytes calldata) external returns (bytes memory);
    
    // Read environment variables as arrays with default value, (name, value[]) => (value[])
    function envOr(string calldata, string calldata, bool[] calldata) external returns (bool[] memory);
    function envOr(string calldata, string calldata, uint256[] calldata) external returns (uint256[] memory);
    function envOr(string calldata, string calldata, int256[] calldata) external returns (int256[] memory);
    function envOr(string calldata, string calldata, address[] calldata) external returns (address[] memory);
    function envOr(string calldata, string calldata, bytes32[] calldata) external returns (bytes32[] memory);
    function envOr(string calldata, string calldata, string[] calldata) external returns (string[] memory);
    function envOr(string calldata, string calldata, bytes[] calldata) external returns (bytes[] memory);

    // Convert Solidity types to strings
    function toString(address) external returns(string memory);
    function toString(bytes calldata) external returns(string memory);
    function toString(bytes32) external returns(string memory);
    function toString(bool) external returns(string memory);
    function toString(uint256) external returns(string memory);
    function toString(int256) external returns(string memory);

    // Sets the *next* call's msg.sender to be the input address
    function prank(address) external;

    // Sets all subsequent calls' msg.sender to be the input address
    // until `stopPrank` is called
    function startPrank(address) external;

    // Sets the *next* call's msg.sender to be the input address,
    // and the tx.origin to be the second input
    function prank(address, address) external;

    // Sets all subsequent calls' msg.sender to be the input address until
    // `stopPrank` is called, and the tx.origin to be the second input
    function startPrank(address, address) external;

    // Resets subsequent calls' msg.sender to be `address(this)`
    function stopPrank() external;

    // Reads the current `msg.sender` and `tx.origin` from state and reports if there is any active caller modification
    function readCallers() external returns (CallerMode callerMode, address msgSender, address txOrigin);

    // Sets an address' balance
    function deal(address who, uint256 newBalance) external;

    // Set the balance of an account for any ERC20 token
    function deal(address token, address to, uint256 give) external;
    
    // Alternative signature to update `totalSupply`
    function deal(address token, address to, uint256 give, bool adjust) external;
    
    // Sets an address' code
    function etch(address who, bytes calldata code) external;

    // Marks a test as skipped. Must be called at the top of the test.
    function skip(bool skip) external;

    // Expects an error on next call
    function expectRevert() external;
    function expectRevert(bytes calldata) external;
    function expectRevert(bytes4) external;

    // Record all storage reads and writes
    function record() external;

    // Gets all accessed reads and write slot from a recording session,
    // for a given address
    function accesses(address)
        external
        returns (bytes32[] memory reads, bytes32[] memory writes);

    // Record all the transaction logs
    function recordLogs() external;

    // Gets all the recorded logs
    function getRecordedLogs() external returns (Log[] memory);

    // Prepare an expected log with the signature:
    //   (bool checkTopic1, bool checkTopic2, bool checkTopic3, bool checkData).
    //
    // Call this function, then emit an event, then call a function.
    // Internally after the call, we check if logs were emitted in the expected order
    // with the expected topics and data (as specified by the booleans)
    //
    // The second form also checks supplied address against emitting contract.
    function expectEmit(bool, bool, bool, bool) external;
    function expectEmit(bool, bool, bool, bool, address) external;

    // Mocks a call to an address, returning specified data.
    //
    // Calldata can either be strict or a partial match, e.g. if you only
    // pass a Solidity selector to the expected calldata, then the entire Solidity
    // function will be mocked.
    function mockCall(address, bytes calldata, bytes calldata) external;

    // Reverts a call to an address, returning the specified error
    //
    // Calldata can either be strict or a partial match, e.g. if you only
    // pass a Solidity selector to the expected calldata, then the entire Solidity
    // function will be mocked.
    function mockCallRevert(address where, bytes calldata data, bytes calldata retdata) external;

    // Clears all mocked and reverted mocked calls
    function clearMockedCalls() external;

    // Expect a call to an address with the specified calldata.
    // Calldata can either be strict or a partial match
    function expectCall(address, bytes calldata) external;
    // Expect a call to an address with the specified
    // calldata and message value.
    // Calldata can either be strict or a partial match
    function expectCall(address, uint256, bytes calldata) external;

    // Gets the _creation_ bytecode from an artifact file. Takes in the relative path to the json file
    function getCode(string calldata) external returns (bytes memory);
    // Gets the _deployed_ bytecode from an artifact file. Takes in the relative path to the json file
    function getDeployedCode(string calldata) external returns (bytes memory);

    // Label an address in test traces
    function label(address addr, string calldata label) external;
    
    // Retrieve the label of an address
    function getLabel(address addr) external returns (string memory);

    // When fuzzing, generate new inputs if conditional not met
    function assume(bool) external;

    // Set block.coinbase (who)
    function coinbase(address) external;

    // Using the address that calls the test contract or the address provided
    // as the sender, has the next call (at this call depth only) create a
    // transaction that can later be signed and sent onchain
    function broadcast() external;
    function broadcast(address) external;

    // Using the address that calls the test contract or the address provided
    // as the sender, has all subsequent calls (at this call depth only) create
    // transactions that can later be signed and sent onchain
    function startBroadcast() external;
    function startBroadcast(address) external;

    // Stops collecting onchain transactions
    function stopBroadcast() external;

    // Reads the entire content of file to string, (path) => (data)
    function readFile(string calldata) external returns (string memory);
    // Get the path of the current project root
    function projectRoot() external returns (string memory);
    // Reads next line of file to string, (path) => (line)
    function readLine(string calldata) external returns (string memory);
    // Writes data to file, creating a file if it does not exist, and entirely replacing its contents if it does.
    // (path, data) => ()
    function writeFile(string calldata, string calldata) external;
    // Writes line to file, creating a file if it does not exist.
    // (path, data) => ()
    function writeLine(string calldata, string calldata) external;
    // Closes file for reading, resetting the offset and allowing to read it from beginning with readLine.
    // (path) => ()
    function closeFile(string calldata) external;
    // Removes file. This cheatcode will revert in the following situations, but is not limited to just these cases:
    // - Path points to a directory.
    // - The file doesn't exist.
    // - The user lacks permissions to remove the file.
    // (path) => ()
    function removeFile(string calldata) external;
    
    // Return the value(s) that correspond to 'key'
    function parseJson(string memory json, string memory key) external returns (bytes memory);
    // Return the entire json file
    function parseJson(string memory json) external returns (bytes memory);

    // Snapshot the current state of the evm.
    // Returns the id of the snapshot that was created.
    // To revert a snapshot use `revertTo`
    function snapshot() external returns (uint256);
    // Revert the state of the evm to a previous snapshot
    // Takes the snapshot id to revert to.
    // This deletes the snapshot and all snapshots taken after the given snapshot id.
    function revertTo(uint256) external returns (bool);

    // Creates a new fork with the given endpoint and block,
    // and returns the identifier of the fork
    function createFork(string calldata, uint256) external returns (uint256);
    // Creates a new fork with the given endpoint and the _latest_ block,
    // and returns the identifier of the fork
    function createFork(string calldata) external returns (uint256);

    // Creates _and_ also selects a new fork with the given endpoint and block,
    // and returns the identifier of the fork
    function createSelectFork(string calldata, uint256)
        external
        returns (uint256);
    // Creates _and_ also selects a new fork with the given endpoint and the
    // latest block and returns the identifier of the fork
    function createSelectFork(string calldata) external returns (uint256);

    // Takes a fork identifier created by `createFork` and
    // sets the corresponding forked state as active.
    function selectFork(uint256) external;

    // Returns the currently active fork
    // Reverts if no fork is currently active
    function activeFork() external returns (uint256);

    // Updates the currently active fork to given block number
    // This is similar to `roll` but for the currently active fork
    function rollFork(uint256) external;
    // Updates the given fork to given block number
    function rollFork(uint256 forkId, uint256 blockNumber) external;

    // Fetches the given transaction from the active fork and executes it on the current state
    function transact(bytes32) external;
    // Fetches the given transaction from the given fork and executes it on the current state
    function transact(uint256, bytes32) external;

    // Marks that the account(s) should use persistent storage across
    // fork swaps in a multifork setup, meaning, changes made to the state
    // of this account will be kept when switching forks
    function makePersistent(address) external;
    function makePersistent(address, address) external;
    function makePersistent(address, address, address) external;
    function makePersistent(address[] calldata) external;
    // Revokes persistent status from the address, previously added via `makePersistent`
    function revokePersistent(address) external;
    function revokePersistent(address[] calldata) external;
    // Returns true if the account is marked as persistent
    function isPersistent(address) external returns (bool);

    /// Returns the RPC url for the given alias
    function rpcUrl(string calldata) external returns (string memory);
    /// Returns all rpc urls and their aliases `[alias, url][]`
    function rpcUrls() external returns (string[2][] memory);
}

Environment

`warp`

Signature

function warp(uint256) external;

Description

Sets block.timestamp.

Examples

vm.warp(1641070800);
emit log_uint(block.timestamp); // 1641070800

`roll`

Signature

function roll(uint256) external;

Description

Sets block.number.

Examples

vm.roll(100);
emit log_uint(block.number); // 100

`fee`

Signature

function fee(uint256) external;

Description

Sets block.basefee.

Examples

vm.fee(25 gwei);
emit log_uint(block.basefee); // 25000000000

`difficulty`

Signature

function difficulty(uint256) external;

Description

Sets block.difficulty.

If used with a post-merge EVM version (Paris and onwards), it will revert. In that case, use vm.prevrandao instead.

Examples

vm.difficulty(25);
emit log_uint(block.difficulty); // 25

`prevrandao`

Signature

function prevrandao(bytes32) external;

Description

Sets block.prevrandao.

If used with an EVM version previous to the Paris hard fork, it will revert. In that case, use vm.difficulty instead.

Examples

vm.prevrandao(bytes32(uint256(42)));
emit log_uint(block.prevrandao); // 42

`chainId`

Signature

function chainId(uint256) external;

Description

Sets block.chainid.

Examples

vm.chainId(31337);
emit log_uint(block.chainid); // 31337

`store`

Signature

function store(address account, bytes32 slot, bytes32 value) external;

Description

Stores the value value in storage slot slot on account account.

Examples

/// contract LeetContract {
///     uint256 private leet = 1337; // slot 0
/// }

vm.store(address(leetContract), bytes32(uint256(0)), bytes32(uint256(31337)));
bytes32 leet = vm.load(address(leetContract), bytes32(uint256(0)));
emit log_uint(uint256(leet)); // 31337

`load`

Signature

function load(address account, bytes32 slot) external returns (bytes32);

Description

Loads the value from storage slot slot on account account.

Examples

/// contract LeetContract {
///     uint256 private leet = 1337; // slot 0
/// }

bytes32 leet = vm.load(address(leetContract), bytes32(uint256(0)));
emit log_uint(uint256(leet)); // 1337

`etch`

Signature

function etch(address who, bytes calldata code) external;

Description

Sets the bytecode of an address who to code.

Examples

bytes memory code = address(awesomeContract).code;
address targetAddr = address(1);
vm.etch(targetAddr, code);
log_bytes(address(targetAddr).code); // 0x6080604052348015610010...

`deal`

Signature

function deal(address who, uint256 newBalance) external;

function deal(address token, address to, uint256 give) external;

function deal(address token, address to, uint256 give, bool adjust) external;

Description

Sets the balance of an address who to newBalance.

If the alternative signature of deal is used, then we can additionaly specify ERC20 token address, as well as an option to update totalSupply.

Examples

address alice = address(1);
vm.deal(alice, 1 ether);
log_uint256(alice.balance); // 1000000000000000000

address alice = address(1);
deal(address(DAI), alice, 1 ether); // import StdUtils.sol first
log_uint256(address(DAI).balanceOf(alice); // 1000000000000000000

`prank`

Signature

function prank(address) external;

function prank(address sender, address origin) external;

Description

Sets msg.sender to the specified address for the next call. "The next call" includes static calls as well, but not calls to the cheat code address.

If the alternative signature of prank is used, then tx.origin is set as well for the next call.

Examples

/// function withdraw() public {
///     require(msg.sender == owner);

vm.prank(owner);
myContract.withdraw(); // [PASS]

`startPrank`

Signature

function startPrank(address) external;

function startPrank(address sender, address origin) external;

Description

Sets msg.sender for all subsequent calls until stopPrank is called.

If the alternative signature of startPrank is used, then tx.origin is set as well for all subsequent calls.

`stopPrank`

Signature

function stopPrank() external;

Description

Stops an active prank started by startPrank, resetting msg.sender and tx.origin to the values before startPrank was called.

`readCallers`

Signature

enum CallerMode {
    None,
    Broadcast,
    RecurrentBroadcast,
    Prank,
    RecurrentPrank
}

function readCallers() 
external 
returns (CallerMode callerMode, address msgSender, address txOrigin);

Description

Reads the current CallerMode, msg.sender, and tx.origin.

The CallerMode enum indicates if there is an active caller modification and the type.

If there is an active prank:
- callerMode will be equal to:
  - CallerMode.Prank if the prank has been set with prank.
  - CallerMode.RecurrentPrank if the prank has been set with startPrank.
If there is an active broadcast:
- callerMode will be equal to:
  - CallerMode.Broadcast if the broadcast has been set with broadcast.
  - CallerMode.RecurrentBroadcast if the broadcast has been set with startBroadcast.
If no caller modification is active:
- callerMode will be equal to CallerMode.None.

Examples

CallerMode callerMode;
address msgSender;
address txOrigin;

// Example 1
(callerMode, msgSender, txOrigin) = vm.readCallers();
assertEq(callerMode, CallerMode.None);
assertEq(msgSender, defaultSenderAddress);
assertEq(txOrigin, defaultOriginAddress);

// Example 2
vm.prank(senderPrankAddress);
(callerMode, msgSender, txOrigin) = vm.readCallers();
assertEq(callerMode, CallerMode.Prank);
assertEq(msgSender, senderPrankAddress);
assertEq(txOrigin, defaultOriginAddress);

// Example 3
vm.prank(senderPrankAddress, originPrankAddress);
(callerMode, msgSender, txOrigin) = vm.readCallers();
assertEq(callerMode, CallerMode.Prank);
assertEq(msgSender, senderPrankAddress);
assertEq(txOrigin, originPrankAddress);

// Example 4
vm.broadcast(broadcastAddress);
(callerMode, msgSender, txOrigin) = vm.readCallers();
assertEq(callerMode, CallerMode.Broadcast);
assertEq(msgSender, broadcastAddress);
assertEq(txOrigin, broadcastAddress);

`record`

Signature

function record() external;

Description

Tell the VM to start recording all storage reads and writes. To access the reads and writes, use accesses.

ℹ️ Note

Every write also counts as an additional read.

Examples

/// contract NumsContract {
///     uint256 public num1 = 100; // slot 0
///     uint256 public num2 = 200; // slot 1
/// }

vm.record();
numsContract.num2();
(bytes32[] memory reads, bytes32[] memory writes) = vm.accesses(
  address(numsContract)
);
emit log_uint(uint256(reads[0])); // 1

`accesses`

Signature

function accesses(
  address
)
external
returns (
  bytes32[] memory reads,
  bytes32[] memory writes
);

Description

Gets all storage slots that have been read (reads) or written to (writes) on an address.

Note that record must be called first.

ℹ️ Note

Every write also counts as an additional read.

Examples

/// contract NumsContract {
///     uint256 public num1 = 100; // slot 0
///     uint256 public num2 = 200; // slot 1
/// }

vm.record();
numsContract.num2();
(bytes32[] memory reads, bytes32[] memory writes) = vm.accesses(
  address(numsContract)
);
emit log_uint(uint256(reads[0])); // 1

`recordLogs`

Signature

function recordLogs() external;

Description

Tells the VM to start recording all the emitted events. To access them, use getRecordedLogs.

Examples

/// event LogCompleted(
///   uint256 indexed topic1,
///   bytes data
/// );

vm.recordLogs();

emit LogCompleted(10, "operation completed");

Vm.Log[] memory entries = vm.getRecordedLogs();

assertEq(entries.length, 1);
assertEq(entries[0].topics[0], keccak256("LogCompleted(uint256,bytes)"));
assertEq(entries[0].topics[1], bytes32(uint256(10)));
assertEq(abi.decode(entries[0].data, (string)), "operation completed");

`getRecordedLogs`

Signature

struct Log {
  bytes32[] topics;
  bytes data;
  address emitter;
}

function getRecordedLogs()
external
returns (
  Log[] memory
);

Description

Gets the emitted events recorded by recordLogs.

This function will consume the recorded logs when called.

Examples

/// event LogTopic1(
///   uint256 indexed topic1,
///   bytes data
/// );

/// event LogTopic12(
///   uint256 indexed topic1,
///   uint256 indexed topic2,
///   bytes data
/// );

/// bytes memory testData0 = "Some data";
/// bytes memory testData1 = "Other data";


// Start the recorder
vm.recordLogs();

emit LogTopic1(10, testData0);
emit LogTopic12(20, 30, testData1);

// Notice that your entries are <Interface>.Log[]
// as opposed to <instance>.Log[]
Vm.Log[] memory entries = vm.getRecordedLogs();

assertEq(entries.length, 2);

// Recall that topics[0] is the event signature
assertEq(entries[0].topics.length, 2);
assertEq(entries[0].topics[0], keccak256("LogTopic1(uint256,bytes)"));
assertEq(entries[0].topics[1], bytes32(uint256(10)));
// assertEq won't compare bytes variables. Try with strings instead.
assertEq(abi.decode(entries[0].data, (string)), string(testData0));

assertEq(entries[1].topics.length, 3);
assertEq(entries[1].topics[0], keccak256("LogTopic12(uint256,uint256,bytes)"));
assertEq(entries[1].topics[1], bytes32(uint256(20)));
assertEq(entries[1].topics[2], bytes32(uint256(30)));
assertEq(abi.decode(entries[1].data, (string)), string(testData1));

// Emit another event
emit LogTopic1(40, testData0);

// Your last read consumed the recorded logs,
// you will only get the latest emitted even after that call
entries = vm.getRecordedLogs();

assertEq(entries.length, 1);

assertEq(entries[0].topics.length, 2);
assertEq(entries[0].topics[0], keccak256("LogTopic1(uint256,bytes)"));
assertEq(entries[0].topics[1], bytes32(uint256(40)));
assertEq(abi.decode(entries[0].data, (string)), string(testData0));

`setNonce`

Signature

function setNonce(address account, uint64 nonce) external;

Description

Sets the nonce of the given account.

The new nonce must be higher than the current nonce of the account.

Examples

vm.setNonce(address(100), 1234);

`getNonce`

Signature

function getNonce(address account) external returns (uint64);

Description

Gets the nonce of the given account.

Examples

uint256 nonce = vm.getNonce(address(100));
emit log_uint(nonce); // 0

`mockCall`

Signature

function mockCall(address where, bytes calldata data, bytes calldata retdata) external;

function mockCall(
    address where,
    uint256 value,
    bytes calldata data,
    bytes calldata retdata
) external;

Description

Mocks all calls to an address where if the call data either strictly or loosely matches data and returns retdata.

When a call is made to where the call data is first checked to see if it matches in its entirety with data. If not, the call data is checked to see if there is a partial match, with the match starting at the first byte of the call data.

If a match is found, then retdata is returned from the call.

Using the second signature we can mock the calls with a specific msg.value. Calldata match takes precedence over msg.value in case of ambiguity.

Mocked calls are in effect until clearMockedCalls is called.

ℹ️ Note

Calls to mocked addresses may revert if there is no code on the address. This is because Solidity inserts an extcodesize check before some contract calls.

To circumvent this, use the etch cheatcode if the mocked address has no code.

ℹ️ Internal calls

This cheatcode does not currently work on internal calls. See issue #432.

Examples

Mocking an exact call:

function testMockCall() public {
    vm.mockCall(
        address(0),
        abi.encodeWithSelector(MyToken.balanceOf.selector, address(1)),
        abi.encode(10)
    );
    assertEq(IERC20(address(0)).balanceOf(address(1)), 10);
}

Mocking an entire function:

function testMockCall() public {
    vm.mockCall(
        address(0),
        abi.encodeWithSelector(MyToken.balanceOf.selector),
        abi.encode(10)
    );
    assertEq(IERC20(address(0)).balanceOf(address(1)), 10);
    assertEq(IERC20(address(0)).balanceOf(address(2)), 10);
}

Mocking a call with a given msg.value:

function testMockCall() public {
    assertEq(example.pay{value: 10}(1), 1);
    assertEq(example.pay{value: 1}(2), 2);
    vm.mockCall(
        address(example),
        10,
        abi.encodeWithSelector(example.pay.selector),
        abi.encode(99)
    );
    assertEq(example.pay{value: 10}(1), 99);
    assertEq(example.pay{value: 1}(2), 2);
}

`mockCallRevert`

Signature

function mockCallRevert(address where, bytes calldata data, bytes calldata retdata) external;

function mockCallRevert(
    address where,
    uint256 value,
    bytes calldata data,
    bytes calldata retdata
) external;

Description

Reverts all calls to an address where if the call data either strictly or loosely matches data and returns retdata.

retdata can be a raw return message or a custom error.

If a match is found, then the call is reverted and retdata is returned.

Using the second signature we can mock the calls with a specific msg.value. Calldata match takes precedence over msg.value in case of ambiguity.

Reverted mock calls are in effect until clearMockedCalls is called.

ℹ️ Internal calls

This cheatcode does not currently work on internal calls. See issue #432.

Examples

Reverting an exact call with a raw error message:

function testMockCallRevert() public {
    vm.mockCallRevert(
        address(0),
        abi.encodeWithSelector(MyToken.balanceOf.selector, address(1)),
        abi.encode("REVERT_MESSAGE")
    );
    vm.expectRevert("REVERT_MESSAGE");
    IERC20(address(0)).balanceOf(address(1));
}

Reverting a call with a custom error:

function testMockCallRevertWithCustomError() public {
    bytes memory customError = abi.encodeWithSelector(TestError.selector, "ERROR_MESSAGE");
    vm.mockCallRevert(
        address(0),
        abi.encodeWithSelector(MyToken.balanceOf.selector, address(1)),
        customError
    );
    vm.expectRevert(customError);
    IERC20(address(0)).balanceOf(address(1));
}

Mocking a call with a given msg.value:

function testMockCallRevertWithValue() public {
    assertEq(example.pay{value: 10}(1), 1);
    assertEq(example.pay{value: 1}(2), 2);
    vm.mockCallRevert(
        address(example),
        10,
        abi.encodeWithSelector(example.pay.selector),
        "ERROR_MESSAGE"
    );
    assertEq(example.pay{value: 1}(2), 2);
    vm.expectRevert("ERROR_MESSAGE");
    assertEq(example.pay{value: 10}(1), 99);
}

`clearMockedCalls`

Signature

function clearMockedCalls() external;

Description

Clears all mocked calls.

`coinbase`

Signature

function coinbase(address) external;

Description

Sets block.coinbase.

Examples

emit log_address(block.coinbase); // 0x0000000000000000000000000000000000000000
vm.coinbase(0xEA674fdDe714fd979de3EdF0F56AA9716B898ec8);
emit log_address(block.coinbase); // 0xea674fdde714fd979de3edf0f56aa9716b898ec8

`broadcast`

Signature

function broadcast() external;

function broadcast(address who) external;

function broadcast(uint256 privateKey) external;

Description

Using the address that calls the test contract or the address / private key provided as the sender, has the next call (at this call depth only and excluding cheatcode calls) create a transaction that can later be signed and sent onchain.

Examples

function deploy() public {
    cheats.broadcast(ACCOUNT_A);
    Test test = new Test();

    // this won't generate tx to sign
    uint256 b = test.t(4);

    // this will
    cheats.broadcast(ACCOUNT_B);
    test.t(2);

    // this also will, using a private key from your environment variables
    cheats.broadcast(vm.envUint("PRIVATE_KEY"));
    test.t(3);
}

`startBroadcast`

Signature

function startBroadcast() external;

function startBroadcast(address who) external;

function startBroadcast(uint256 privateKey) external;

Description

Using the address that calls the test contract or the address / private key provided as the sender, has all subsequent calls (at this call depth only and excluding cheatcode calls) create transactions that can later be signed and sent onchain.

Examples

function t(uint256 a) public returns (uint256) {
    uint256 b = 0;
    emit log_string("here");
    return b;
}

function deployOther() public {
    vm.startBroadcast(ACCOUNT_A);
    Test test = new Test();
    
    // will trigger a transaction
    test.t(1);
    
    vm.stopBroadcast();

    // broadcast again, this time using a private key from your environment variables
    vm.startBroadcast(vm.envUint("PRIVATE_KEY"));
    test.t(3);
    vm.stopBroadcast();
}

`stopBroadcast`

Signature

function stopBroadcast() external;

Description

Stops collecting transactions for later on-chain broadcasting.

Examples

function deployNoArgs() public {
    // broadcast the next call
    cheats.broadcast();
    Test test1 = new Test();

    // broadcast all calls between this line and `stopBroadcast`
    cheats.startBroadcast();
    Test test2 = new Test();
    cheats.stopBroadcast();
}

`pauseGasMetering`

Signature

function pauseGasMetering() external;

Description

Pauses gas metering (i.e. gasleft() does not decrease as operations are executed).

This can be useful for getting a better sense of gas costs, by turning off gas metering for unnecessary code, as well as long-running scripts that would otherwise run out of gas.

ℹ️ Note

pauseGasMetering turns off DoS protections that come from metering gas usage.

Exposing a service that assumes a particular instance of the EVM will complete due to gas usage no longer is true, and a timeout should be enabled in that case.

`resumeGasMetering`

Signature

function resumeGasMetering() external;

Description

Resumes gas metering (i.e. gasleft() will decrease as operations are executed). Gas usage will resume at the same amount at which it was paused.

`txGasPrice`

Signature

function txGasPrice(uint256) external;

function txGasPrice(uint256 newGasPrice) external;

Description

Sets tx.gasprice for the rest of the transaction.

Examples

We can use this to get accurate gas usage for a transaction.

function testCalculateGas() public {
    vm.txGasPrice(2);
    uint256 gasStart = gasleft();
    myContract.doStuff();
    uint256 gasEnd = gasleft();
    uint256 gasUsed = (gasStart - gasEnd) * tx.gasprice; // tx.gasprice is now 2
}

Assertions

`expectRevert`

Signature

function expectRevert() external;

function expectRevert(bytes4 message) external;

function expectRevert(bytes calldata message) external;

Description

If the next call does not revert with the expected data message, then expectRevert will.

After calling expectRevert, calls to other cheatcodes before the reverting call are ignored.

This means, for example, we can call prank immediately before the reverting call.

There are 3 signatures:

Without parameters: Asserts that the next call reverts, regardless of the message.
With bytes4: Asserts that the next call reverts with the specified 4 bytes.
With bytes: Asserts that the next call reverts with the specified bytes.

⚠️ Gotcha: Usage with low-level calls

Normally, a call that succeeds returns a status of true (along with any return data) and a call that reverts returns false.

The Solidity compiler will insert checks that ensures that the call succeeded, and revert if it did not.

On low level calls, the expectRevert cheatcode works by making the status boolean returned by the low level call correspond to whether the expectRevert succeeded or not, NOT whether or not the low-level call succeeds. Therefore, status being false corresponds to the cheatcode failing.

Apart from this, expectRevert also mangles return data on low level calls, and is not usable.

See the following example. For clarity, status has been renamed to revertsAsExpected:
function testLowLevelCallRevert() public {
    vm.expectRevert(bytes("error message"));
    (bool revertsAsExpected, ) = address(myContract).call(myCalldata);
    assertTrue(revertsAsExpected, "expectRevert: call did not revert");
}

Examples

To use expectRevert with a string, pass it as a string literal.

vm.expectRevert("error message");

To use expectRevert with a custom error type without parameters, use its selector.

vm.expectRevert(CustomError.selector);

To use expectRevert with a custom error type with parameters, ABI encode the error type.

vm.expectRevert(
    abi.encodeWithSelector(CustomError.selector, 1, 2)
);

If you need to assert that a function reverts without a message, you can do so with expectRevert(bytes("")).

function testExpectRevertNoReason() public {
    Reverter reverter = new Reverter();
    vm.expectRevert(bytes(""));
    reverter.revertWithoutReason();
}

Message-less reverts happen when there is an EVM error, such as when the transaction consumes more than the block's gas limit.

If you need to assert that a function reverts a four character message, e.g. AAAA, you can do so with:

function testFourLetterMessage() public {
    vm.expectRevert(bytes("AAAA"));
}

If used expectRevert("AAAA"), the compiler would throw an error because it wouldn't know which overload to use.

Finally, you can also have multiple expectRevert() checks in a single test.

function testMultipleExpectReverts() public {
    vm.expectRevert("INVALID_AMOUNT");
    vault.send(user, 0);

    vm.expectRevert("INVALID_ADDRESS");
    vault.send(address(0), 200);
}

`expectEmit`

Signature

function expectEmit() external;

function expectEmit(
    bool checkTopic1,
    bool checkTopic2,
    bool checkTopic3,
    bool checkData
) external;

function expectEmit(address emitter) external;

function expectEmit(
    bool checkTopic1,
    bool checkTopic2,
    bool checkTopic3,
    bool checkData,
    address emitter
) external;

Description

Assert a specific log is emitted during the next call.

Call the cheat code, specifying whether we should check the first, second or third topic, and the log data (expectEmit() checks them all). Topic 0 is always checked.
Emit the event we are supposed to see during the next call.
Perform the call.

You can perform steps 1 and 2 multiple times to match a sequence of events in the next call.

If the event is not available in the current scope (e.g. if we are using an interface, or an external smart contract), we can define the event ourselves with an identical event signature.

There are 2 varieties of expectEmit:

Without checking the emitter address: Asserts the topics match without checking the emitting address.
With address: Asserts the topics match and that the emitting address matches.

ℹ️ Matching sequences

In functions that emit a lot of events, it's possible to "skip" events and only match a specific sequence, but this sequence must always be in order. As an example, let's say a function emits events: A, B, C, D, E, F, F, G.

expectEmit will be able to match ranges with and without skipping events in between:

[A, B, C] is valid.

[B, D, F] is valid.

[G] or any other single event combination is valid.

[B, A] or similar out-of-order combinations are invalid (events must be in order).

[C, F, F] is valid.

[F, F, C] is invalid (out of order).

Examples

This does not check the emitting address.

event Transfer(address indexed from, address indexed to, uint256 amount);

function testERC20EmitsTransfer() public {
    vm.expectEmit();

    // We emit the event we expect to see.
    emit MyToken.Transfer(address(this), address(1), 10);

    // We perform the call.
    myToken.transfer(address(1), 10);
}

This does check the emitting address.

event Transfer(address indexed from, address indexed to, uint256 amount);

function testERC20EmitsTransfer() public {
    // We check that the token is the event emitter by passing the address.
    vm.expectEmit(address(myToken));
    emit MyToken.Transfer(address(this), address(1), 10);

    // We perform the call.
    myToken.transfer(address(1), 10);
}

We can also assert that multiple events are emitted in a single call.

function testERC20EmitsBatchTransfer() public {
    // We declare multiple expected transfer events
    for (uint256 i = 0; i < users.length; i++) {
        // Here we use the longer signature for demonstration purposes. This call checks
        // topic0 (always checked), topic1 (true), topic2 (true), NOT topic3 (false), and data (true).
        vm.expectEmit(true, true, false, true);
        emit Transfer(address(this), users[i], 10);
    }

    // We also expect a custom `BatchTransfer(uint256 numberOfTransfers)` event.
    vm.expectEmit(false, false, false, true);
    emit BatchTransfer(users.length);

    // We perform the call.
    myToken.batchTransfer(users, 10);
}

This example fails, as the expected event is not emitted on the next call.

event Transfer(address indexed from, address indexed to, uint256 amount);

function testERC20EmitsTransfer() public {
    // We check that the token is the event emitter by passing the address as the fifth argument.
    vm.expectEmit(true, true, false, true, address(myToken));
    emit MyToken.Transfer(address(this), address(1), 10);

    // We perform an unrelated call that won't emit the intended event,
    // making the cheatcode fail.
    myToken.approve(address(this), 1e18);
    // We perform the call, but it will have no effect as the cheatcode has already failed.
    myToken.transfer(address(1), 10);
}

`expectCall`

function expectCall(address where, bytes calldata data) external;

function expectCall(address where, bytes calldata data, uint64 count) external;

function expectCall(
    address where,
    uint256 value,
    bytes calldata data
) external;

function expectCall(
    address where,
    uint256 value,
    bytes calldata data,
    uint64 count
) external;

Description

Expects that a call to a specified address where, where the call data either strictly or loosely matches data. The cheatcode can be called in two ways:

If no count parameter is specified, the call will be expected to be made at least the amount of times the cheatcode was called. For the same calldata, you cannot call the cheatcode with no count and then pass in a count parameter.
If count is specified, the call will be expected to be made strictly count times. For the same calldata, the count value cannot be overwritten with another cheatcode call, nor it can be increment by calling the cheatcode without a count parameter.

count can also be set to 0 to assert that a call is not made.

Using the second signature we can also check if the call was made with the expected msg.value.

If the test terminates without the call being made, the test fails.

ℹ️ Internal calls

This cheatcode does not currently work on internal calls. See issue #432.

Examples

Expect that transfer is called on a token MyToken one time:

address alice = address(10);
vm.expectCall(
  address(token), abi.encodeCall(token.transfer, (alice, 10))
);
token.transfer(alice, 10);
// [PASS]

Expect that transfer is called on a token MyToken at least two times:

address alice = address(10);
vm.expectCall(
  address(token), abi.encodeCall(token.transfer, (alice, 10))
);
vm.expectCall(
  address(token), abi.encodeCall(token.transfer, (alice, 10))
);
token.transfer(alice, 10);
token.transfer(alice, 10);
token.transfer(alice, 10);
// [PASS]

Expect that transfer is not called on a token MyToken:

address alice = address(10);
vm.expectCall(
  address(token), abi.encodeCall(token.transfer, (alice, 10)), 0
);
token.transferFrom(alice, address(0), 10);
// [PASS]

Expect that transfer with any calldata is called on a token MyToken 2 times:

address alice = address(10);
vm.expectCall(
  address(token), abi.encodeWithSelector(token.transfer), 2
);
token.transfer(alice, 10);
token.transfer(alice, 10);
// [PASS]

Expect that pay is called on a Contract with a specific msg.value and calldata:

Contract target = new Contract();
vm.expectCall(
            address(target),
            1,
            abi.encodeWithSelector(target.pay.selector, 2)
        );
target.pay{value: 1}(2);
// [PASS]

Expect that pay is called on a Contract with a specific msg.value and calldata 3 times:

Contract target = new Contract();
vm.expectCall(
            address(target),
            1,
            abi.encodeWithSelector(target.pay.selector, 2),
            3
        );
target.pay{value: 1}(2);
target.pay{value: 1}(2);
target.pay{value: 1}(2);
// [PASS]

Fuzzer

assume

`assume`

Signature

function assume(bool) external;

Description

If the boolean expression evaluates to false, the fuzzer will discard the current fuzz inputs and start a new fuzz run.

The assume cheatcode should mainly be used for very narrow checks. Broad checks will slow down tests as it will take a while to find valid values, and the test may fail if you hit the max number of rejects.

You can configure the rejection thresholds by setting fuzz.max_test_rejects in your foundry.toml file.

For broad checks, such as ensuring a uint256 falls within a certain range, you can bound your input with the modulo operator or Forge Standard's bound method.

More information on filtering via assume can be found here.

Examples

// Good example of using assume
function testSomething(uint256 a) public {
    vm.assume(a != 1);
    require(a != 1);
    // [PASS]
}

// In this case assume is not a great fit, so you should bound inputs manually
function testSomethingElse(uint256 a) public {
    a = bound(a, 100, 1e36);
    require(a >= 100 && a <= 1e36);
    // [PASS]
}

Forking

`createFork`

Signature

// Creates a new fork with the given endpoint and the _latest_ block and returns the identifier of the fork
function createFork(string calldata urlOrAlias) external returns (uint256)

// Creates a new fork with the given endpoint and block and returns the identifier of the fork
function createFork(string calldata urlOrAlias, uint256 block) external returns (uint256);

// Creates a new fork with the given endpoint and at the block the given transaction was mined in, and replays all transaction mined in the block before the transaction
function createFork(string calldata urlOrAlias, bytes32 transaction) external returns (uint256);

Description

Creates a new fork from the given endpoint and returns the identifier of the fork. If a block number is passed as an argument, the fork will begin on that block, otherwise it will begin on the latest block.

If a transaction hash is provided, it will roll the fork to the block the transaction was mined in and replays all previously executed transactions.

Examples

Create a new mainnet fork with the latest block number:

uint256 forkId = vm.createFork(MAINNET_RPC_URL);
vm.selectFork(forkId);

assertEq(block.number, 15_171_037); // as of time of writing, 2022-07-19 04:55:27 UTC

Create a new mainnet fork with a given block number:

uint256 forkId = vm.createFork(MAINNET_RPC_URL, 1_337_000);
vm.selectFork(forkId);

assertEq(block.number, 1_337_000);

`selectFork`

Signature

function selectFork(uint256 forkId) external;

Description

Takes a fork identifier created by createFork and sets the corresponding forked state as active.

Examples

Select a previously created fork:

uint256 forkId = vm.createFork(MAINNET_RPC_URL);

vm.selectFork(forkId);

assertEq(vm.activeFork(), forkId);

`createSelectFork`

Signature

function createSelectFork(string calldata urlOrAlias) external returns (uint256);

function createSelectFork(string calldata urlOrAlias, uint256 block) external returns (uint256);

function createSelectFork(string calldata urlOrAlias, bytes32 transaction) external returns (uint256);

Description

Creates and selects a new fork from the given endpoint and returns the identifier of the fork. If a block number is passed as an argument, the fork will begin on that block, otherwise it will begin on the latest block.

If a transaction hash is provided, it will roll the fork to the block the transaction was mined in and replays all previously executed transactions.

Examples

Create and select a new mainnet fork with the latest block number:

uint256 forkId = vm.createSelectFork(MAINNET_RPC_URL);

assertEq(block.number, 15_171_037); // as of time of writing, 2022-07-19 04:55:27 UTC

Create and select a new mainnet fork with a given block number:

uint256 forkId = vm.createSelectFork(MAINNET_RPC_URL, 1_337_000);

assertEq(block.number, 1_337_000);

`activeFork`

Signature

function activeFork() external returns (uint256);

Description

Returns the identifier for the currently active fork. Reverts if no fork is currently active.

Examples

Get the currently active fork id:

uint256 mainnetForkId = vm.createFork(MAINNET_RPC_URL);
uint256 optimismForkId = vm.createFork(OPTIMISM_RPC_URL);

assert(mainnetForkId != optimismForkId);

vm.selectFork(mainnetForkId);
assertEq(vm.activeFork(), mainnetForkId);

vm.selectFork(optimismForkId);
assertEq(vm.activeFork(), optimismForkId);

`rollFork`

Signature

// roll the _active_ fork to the given block
function rollFork(uint256 blockNumber) external;

// roll the _active_ fork to the block in which the transaction was mined it and replays all previously executed transactions
function rollFork(bytes32 transaction) external;

// Same as `rollFork(uint256 blockNumber)` but uses the fork corresponding to the `forkId`
function rollFork(uint256 forkId, uint256 blockNumber) external;

// Same as `rollFork(bytes32 transaction)` but uses the fork corresponding to the `forkId`
function rollFork(uint256 forkId, bytes32 transaction) external;

Description

Sets block.number. If a fork identifier is passed as an argument, it will update that fork, otherwise it will update the currently active fork.

If a transaction hash is provided, it will roll the fork to the block the transaction was mined in and replays all previously executed transactions.

Examples

Set block.number for the currently active fork:

uint256 forkId = vm.createFork(MAINNET_RPC_URL);
vm.selectFork(forkId);

assertEq(block.number, 15_171_037); // as of time of writing, 2022-07-19 04:55:27 UTC

vm.rollFork(15_171_057);

assertEq(block.number, 15_171_057);

Set block.number for the fork identified by the passed forkId argument:

uint256 optimismForkId = vm.createFork(OPTIMISM_RPC_URL);

vm.rollFork(optimismForkId, 1_337_000);

vm.selectFork(optimismForkId);

assertEq(block.number, 1_337_000);

`makePersistent`

Signature

function makePersistent(address account) external;
function makePersistent(address account0, address account1) external;
function makePersistent(address account0, address account1, address account2) external;
function makePersistent(address[] calldata accounts) external;

Description

Each fork (createFork) has its own independent storage, which is also replaced when another fork is selected (selectFork). By default, only the test contract account and the caller are persistent across forks, which means that changes to the state of the test contract (variables) are preserved when different forks are selected. This way data can be shared by storing it in the contract's variables.

However, with this cheatcode, it is possible to mark the specified accounts as persistent, which means that their state is available regardless of which fork is currently active.

Examples

Mark a new contract as persistent

contract SimpleStorageContract {
    string public value;

    function set(uint256 _value) public {
        value = _value;
    }
}

function testMarkPersistent() public {
    // by default the `sender` and the contract itself are persistent
    assert(cheats.isPersistent(msg.sender));
    assert(cheats.isPersistent(address(this)));

    // select a specific fork
    cheats.selectFork(mainnetFork);
    
    // create a new contract that's stored in the `mainnetFork` storage
    SimpleStorageContract simple = new SimpleStorageContract();
    
    // `simple` is not marked as persistent
    assert(!cheats.isPersistent(address(simple)));
    
    // contract can be used
    uint256 expectedValue = 99;
    simple.set(expectedValue);
    assertEq(simple.value(), expectedValue);
    
    // mark as persistent
    cheats.makePersistent(address(simple));
    
    // select a different fork
    cheats.selectFork(optimismFork);
    
    // ensure contract is still persistent   
    assert(cheats.isPersistent(address(simple)));
    
    // value is set as expected
    assertEq(simple.value(), expectedValue);
}

`revokePersistent`

Signature

function revokePersistent(address) external;
function revokePersistent(address[] calldata) external;

Description

The counterpart of makePersistent, that makes the given contract not persistent across fork swaps

Examples

Revoke a persistent status of a contract

contract SimpleStorageContract {
    string public value;

    function set(uint256 _value) public {
        value = _value;
    }
}

function testRevokePersistent() public {
    // select a specific fork
    cheats.selectFork(mainnetFork);
    
    // create a new contract that's stored in the `mainnetFork` storage
    SimpleStorageContract simple = new SimpleStorageContract();
    
    // `simple` is not marked as persistent
    assert(!cheats.isPersistent(address(simple)));
       
    // make it persistent
    cheats.makePersistent(address(simple));
    
    // ensure it is persistent
    assert(cheats.isPersistent(address(simple)));
    
    // revoke it
    cheats.revokePersistent(address(simple));
    
    // contract no longer persistent
    assert(!cheats.isPersistent(address(simple)));
}

`isPersistent`

Signature

function isPersistent(address) external returns (bool);

Description

Returns whether an account is marked as persistent (makePersistent).

Examples

Check default status of msg.sender and the current test account

// By default the `sender` and the test contract itself are persistent
assert(cheats.isPersistent(msg.sender));
assert(cheats.isPersistent(address(this)));

`allowCheatcodes`

Signature

function allowCheatcodes(address) external;

Description

In forking mode, explicitly grant the given address cheatcode access.

By default, the test contract, and its deployer are allowed to access cheatcodes. In addition to that, cheat code access is granted if the contract was deployed by an address that already has cheatcode access. This will prevent cheatcode access from accounts already deployed on the forked network.

ℹ️ Note

This is only useful for more complex test setups in forking mode.

`transact`

Signature

// Fetches the given transaction from the active fork and executes it on the current state
function transact(bytes32 txHash) external;
// Fetches the given transaction from the given fork and executes it on the current state
function transact(uint256 forkId, bytes32 txHash) external;

Description

In forking mode, fetches the Transaction from the provider and executes it on the current state

Examples

Enter forking mode and execute a transaction:

// Enter forking mode at block: https://etherscan.io/block/15596646
uint256 fork = vm.createFork(MAINNET_RPC_URL, 15596646);
vm.selectFork(fork);

// a random transfer transaction in the block: https://etherscan.io/tx/0xaba74f25a17cf0d95d1c6d0085d6c83fb8c5e773ffd2573b99a953256f989c89
bytes32 tx = 0xaba74f25a17cf0d95d1c6d0085d6c83fb8c5e773ffd2573b99a953256f989c89;

address sender = address(0xa98218cdc4f63aCe91ddDdd24F7A580FD383865b);
address recipient = address(0x0C124046Fa7202f98E4e251B50488e34416Fc306);

assertEq(sender.balance, 5764124000000000);
assertEq(recipient.balance, 3936000000000000);

// transfer amount: 0.003936 Ether
uint256 transferAmount = 3936000000000000;

// expected balance changes once the transaction is executed
uint256 expectedRecipientBalance = recipient.balance + transferAmount;
uint256 expectedSenderBalance = sender.balance - transferAmount;

// execute the transaction
vm.transact(tx);

// recipient received transfer
assertEq(recipient.balance, expectedRecipientBalance);

// sender's balance decreased by transferAmount and gas
assert(sender.balance < expectedSenderBalance);

External

`ffi`

Signature

function ffi(string[] calldata) external returns (bytes memory);

Description

Calls an arbitrary command if ffi is enabled.

It is generally advised to use this cheat code as a last resort, and to not enable it by default, as anyone who can change the tests of a project will be able to execute arbitrary commands on devices that run the tests.

Tips

By default the ffi cheatcode assumes the output of the command is a hex encoded value (e.g. a hex string of an ABI encoded value). If hex decoding fails, it will return the output as UTF8 bytes that you can cast to a string.
Make sure that the output does not include a \n newline character. (e.g in Rust use print! vs println!)
Remember that the script will be executed from the top-level directory of your project, not inside test
Make sure that the inputs array does not have empty elements. They will be handled as inputs by the script, instead of space
Use the cheatcode toString to easily convert arbitrary data to strings, so that you can pass them as command-line arguments

Examples

ABI encoded output

string[] memory inputs = new string[](3);
inputs[0] = "echo";
inputs[1] = "-n";
// ABI encoded "gm", as a hex string
inputs[2] = "0x00000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000002676d000000000000000000000000000000000000000000000000000000000000";

bytes memory res = vm.ffi(inputs);
string memory output = abi.decode(res, (string));
assertEq(output, "gm");

UTF8 string output

string[] memory inputs = new string[](3);
inputs[0] = "echo";
inputs[1] = "-n";
inputs[2] = "gm";

bytes memory res = vm.ffi(inputs);
assertEq(string(res), "gm");

`projectRoot`

Signature

function projectRoot() external returns (string memory);

Description

Returns the root directory of the current Foundry project.

`getCode`

Signature

function getCode(string calldata) external returns (bytes memory);

Description

Returns the creation bytecode for a contract in the project given the path to the contract.

The calldata parameter can either be in the form ContractFile.sol (if the filename and contract name are the same), ContractFile.sol:ContractName, or the path to an artifact, relative to the root of your project.

ℹ️ Note

getCode requires read permission for the output directory, see file cheatcodes.

To grant read access set fs_permissions = [{ access = "read", path = "./out"}] in your foundry.toml.

Examples

MyContract myContract = new MyContract(arg1, arg2);

// Let's do the same thing with `getCode`
bytes memory args = abi.encode(arg1, arg2);
bytes memory bytecode = abi.encodePacked(vm.getCode("MyContract.sol:MyContract"), args);
address anotherAddress;
assembly {
    anotherAddress := create(0, add(bytecode, 0x20), mload(bytecode))
}

assertEq0(address(myContract).code, anotherAddress.code); // [PASS]

Deploy a contract to an arbitrary address by combining getCode and etch

// Deploy
bytes memory args = abi.encode(arg1, arg2);
bytes memory bytecode = abi.encodePacked(vm.getCode("MyContract.sol:MyContract"), args);
address deployed;
assembly {
    deployed := create(0, add(bytecode, 0x20), mload(bytecode))
}

// Set the bytecode of an arbitrary address
vm.etch(targetAddr, deployed.code);

`getDeployedCode`

Signature

function getDeployedCode(string calldata) external returns (bytes memory);

Description

This cheatcode works similar to getCode but only returns the deployed bytecode (aka runtime bytecode) for a contract in the project given the path to the contract.

The main use case for this cheat code is as a shortcut to deploy stateless contracts to arbitrary addresses.

The calldata parameter can either be in the form ContractFile.sol (if the filename and contract name are the same) , ContractFile.sol:ContractName, or the path to an artifact, relative to the root of your project.

ℹ️ Note

getDeployedCode requires read permission for the output directory, see file cheatcodes.

To grant read access set fs_permissions = [{ access = "read", path = "./out"}] in your foundry.toml.

Examples

Deploy a stateless contract at an arbitrary address using getDeployedCode and etch.

// A stateless contract that we want deployed at a specific address
contract Override {
    event Payload(address sender, address target, bytes data);

    function emitPayload(
        address target, bytes calldata message
    ) external payable returns (uint256) {
        emit Payload(msg.sender, target, message);
        return 0;
    }
}

// get the **deployedBytecode**
bytes memory code = vm.getDeployedCode("Override.sol:Override");

// set the code of an arbitrary address
address overrideAddress = address(64);
vm.etch(overrideAddress, code);
assertEq(overrideAddress.code, code);

`setEnv`

Signature

function setEnv(string calldata key, string calldata value) external;

Description

Set an environment variable key=value.

ℹ️ Note

Environment variables set by a process are only accessible by itself and its child processes. Thus, calling setEnv will only modify environment variables of the currently running forge process, and won't affect the shell (forge's parent process), i.e., the they won't persist after the forge process exit.

Tips

The environment variable key can't be empty.
The environment variable key can't contain the equal sign = or the NUL character \0.
The environment variable value can't contain the NUL character \0.

Examples

string memory key = "hello";
string memory val = "world";
cheats.setEnv(key, val);

`envOr`

Signature

function envOr(string calldata key, bool defaultValue) external returns (bool value);
function envOr(string calldata key, uint256 defaultValue) external returns (uint256 value);
function envOr(string calldata key, int256 defaultValue) external returns (int256 value);
function envOr(string calldata key, address defaultValue) external returns (address value);
function envOr(string calldata key, bytes32 defaultValue) external returns (bytes32 value);
function envOr(string calldata key, string calldata defaultValue) external returns (string memory value);
function envOr(string calldata key, bytes calldata defaultValue) external returns (bytes memory value);

function envOr(string calldata key, string calldata delimiter, bool[] calldata defaultValue) external returns (bool[] memory value);
function envOr(string calldata key, string calldata delimiter, uint256[] calldata defaultValue) external returns (uint256[] memory value);
function envOr(string calldata key, string calldata delimiter, int256[] calldata defaultValue) external returns (int256[] memory value);
function envOr(string calldata key, string calldata delimiter, address[] calldata defaultValue) external returns (address[] memory value);
function envOr(string calldata key, string calldata delimiter, bytes32[] calldata defaultValue) external returns (bytes32[] memory value);
function envOr(string calldata key, string calldata delimiter, string[] calldata defaultValue) external returns (string[] memory value);
function envOr(string calldata key, string calldata delimiter, bytes[] calldata defaultValue) external returns (bytes[] memory value);

Description

A non-failing way to read an environment variable of any type: if the requested environment key does not exist, envOr() will return a default value instead of reverting (works with arrays too).

The returned type is determined by the type of defaultValue parameter passed.

Tips

Use envOr(key, defaultValue) to read a single value
Use envOr(key, delimiter, defaultValue[]) to read an array with delimiter
The parsing of the environment variable will be done according to the type of defaultValue (e.g. if the default value type is uint - the environment variable will be also parsed as uint)
Use explicit casting for literals to specify type of default variable: uint(69) will return an uint but int(69) will return an int
Same with: string("") and bytes("") - these will return string and bytes accordingly
Use dynamic arrays (bool[]) instead of fixed-size arrays (bool[4]) when providing default values (only dynamic arrays are supported)

Examples

Single Value

If the environment variable FORK is not set, you can specify it to be false by default:

bool fork = vm.envOr("FORK", false);

address owner;

function setUp() {
  owner = vm.envOr("OWNER", address(this));
}

Array

If the environment variable BAD_TOKENS is not set, you can specify the default to be an empty array:

address[] badTokens;

function envBadTokens() public {
  badTokens = vm.envOr("BAD_TOKENS", ",", badTokens);
}

function envBadTokens() public {
  address[] memory defaultBadTokens = new address[](0);
  address[] memory badTokens = vm.envOr("BAD_TOKENS", ",", defaultBadTokens);
}

`envBool`

Signature

function envBool(string calldata key) external returns (bool value);

function envBool(string calldata key, string calldata delimiter) external returns (bool[] memory values);

Description

Read an environment variable as bool or bool[].

Tips

For true, use either "true" or "True" for the environment variable value.
For false, use either "false" or "False" for the environment variable value.
For arrays, you can specify the delimiter used to seperate the values with the delimiter parameter.

Examples

Single Value

With environment variable BOOL_VALUE=true,

string memory key = "BOOL_VALUE";
bool expected = true;
bool output = cheats.envBool(key);
assert(output == expected);

Array

With environment variable BOOL_VALUES=true,false,True,False,

string memory key = "BOOL_VALUES";
string memory delimiter = ",";
bool[4] memory expected = [true, false, true, false];
bool[] memory output = cheats.envBool(key, delimiter);
assert(keccak256(abi.encodePacked((output))) == keccak256(abi.encodePacked((expected))));

`envUint`

Signature

function envUint(string calldata key) external returns (uint256 value);

function envUint(string calldata key, string calldata delimiter) external returns (uint256[] memory values);

Description

Read an environment variable as uint256 or uint256[].

Tips

If the value starts with 0x, it will be interpreted as a hex value, otherwise, it will be treated as a decimal number.
For arrays, you can specify the delimiter used to seperate the values with the delimiter parameter.

Examples

Single Value

With environment variable UINT_VALUE=115792089237316195423570985008687907853269984665640564039457584007913129639935,

string memory key = "UINT_VALUE";
uint256 expected = type(uint256).max;
uint256 output = cheats.envUint(key);
assert(output == expected);

Array

With environment variable UINT_VALUES=0,0x0000000000000000000000000000000000000000000000000000000000000000,

string memory key = "UINT_VALUES";
string memory delimiter = ",";
uint256[2] memory expected = [type(uint256).min, type(uint256).min];
uint256[] memory output = cheats.envUint(key, delimiter);
assert(keccak256(abi.encodePacked((output))) == keccak256(abi.encodePacked((expected))));

`envInt`

Signature

function envInt(string calldata key) external returns (int256 value);

function envInt(string calldata key, string calldata delimiter) external returns (int256[] memory values);

Description

Read an environment variable as int256 or int256[].

Tips

If the value starts with 0x, -0x or +0x, it will be interpreted as a hex value, otherwise, it will be treated as a decimal number.
For arrays, you can specify the delimiter used to seperate the values with the delimiter parameter.

Examples

Single Value

With environment variable INT_VALUE=-57896044618658097711785492504343953926634992332820282019728792003956564819968,

string memory key = "INT_VALUE";
int256 expected = type(int256).min;
int256 output = cheats.envInt(key);
assert(output == expected);

Array

With environment variable INT_VALUES=-0x8000000000000000000000000000000000000000000000000000000000000000,+0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF,

string memory key = "INT_VALUES";
string memory delimiter = ",";
int256[2] memory expected = [type(int256).min, type(int256).max];
int256[] memory output = cheats.envInt(key, delimiter);
assert(keccak256(abi.encodePacked((output))) == keccak256(abi.encodePacked((expected))));

`envAddress`

Signature

function envAddress(string calldata key) external returns (address value);

function envAddress(string calldata key, string calldata delimiter) external returns (address[] memory values);

Description

Read an environment variable as address or address[].

Tips

For arrays, you can specify the delimiter used to seperate the values with the delimiter parameter.

Examples

Single Value

With environment variable ADDRESS_VALUE=0x7109709ECfa91a80626fF3989D68f67F5b1DD12D,

string memory key = "ADDRESS_VALUE";
address expected = 0x7109709ECfa91a80626fF3989D68f67F5b1DD12D;
address output = cheats.envAddress(key);
assert(output == expected);

Array

With environment variable ADDRESS_VALUES=0x7109709ECfa91a80626fF3989D68f67F5b1DD12D,0x0000000000000000000000000000000000000000,

string memory key = "ADDRESS_VALUES";
string memory delimiter = ",";
address[2] memory expected = [
    0x7109709ECfa91a80626fF3989D68f67F5b1DD12D,
    0x0000000000000000000000000000000000000000
];
address[] memory output = cheats.envAddress(key, delimiter);
assert(keccak256(abi.encodePacked((output))) == keccak256(abi.encodePacked((expected))));

`envBytes32`

Signature

function envBytes32(string calldata key) external returns (bytes32 value);

function envBytes32(string calldata key, string calldata delimiter) external returns (bytes32[] memory values);

Description

Read an environment variable as bytes32 or address[].

Tips

For arrays, you can specify the delimiter used to seperate the values with the delimiter parameter.

Examples

Single Value

With environment variable BYTES32_VALUE=0x00,

string memory key = "BYTES32_VALUE";
bytes32 expected = bytes32(0x0000000000000000000000000000000000000000000000000000000000000000);
bytes32 output = cheats.envBytes32(key);
assert(output == expected);

Array

With environment variable BYTES32_VALUES=0x7109709ECfa91a80626fF3989D68f67F5b1DD12D,0x00,

string memory key = "BYTES32_VALUES";
string memory delimiter = ",";
bytes32[2] memory expected = [
    bytes32(0x7109709ECfa91a80626fF3989D68f67F5b1DD12D000000000000000000000000),
    bytes32(0x0000000000000000000000000000000000000000000000000000000000000000)
];
bytes32[] memory output = cheats.envBytes32(key, delimiter);
assert(keccak256(abi.encodePacked((output))) == keccak256(abi.encodePacked((expected))));

`envString`

Signature

function envString(string calldata key) external returns (string value);

function envString(string calldata key, string calldata delimiter) external returns (string[] memory values);

Description

Read an environment variable as string or string[]. In case the environment variable is not defined, Forge will fail with the following error message:

[FAIL. Reason: Failed to get environment variable FOO as type string: environment variable not found]

Tips

You can put your environment variables in a .env file. Forge will automatically load them when running forge test.
For arrays, you can specify the delimiter used to separate the values with the delimiter parameter.
Choose a delimiter that doesn't appear in the string values, so that they can be correctly separated.

Examples

Single Value

With environment variable STRING_VALUE=hello, world!,

string memory key = "STRING_VALUE";
string expected = "hello, world!";
string output = cheats.envString(key);
assertEq(output, expected);

Array

With environment variable STRING_VALUES=hello, world!|0x7109709ECfa91a80626fF3989D68f67F5b1DD12D;

string memory key = "STRING_VALUES";
string memory delimiter = "|";
string[2] memory expected = [
    "hello, world!",
    "0x7109709ECfa91a80626fF3989D68f67F5b1DD12D"
];
string[] memory output = cheats.envString(key, delimiter);
for (uint i = 0; i < expected.length; ++i) {
    assert(keccak256(abi.encodePacked((output[i]))) == keccak256(abi.encodePacked((expected[i]))));
}

`envBytes`

Signature

function envBytes(bytes calldata key) external returns (bytes value);

function envBytes(bytes calldata key, bytes calldata delimiter) external returns (bytes[] memory values);

Description

Read an environment variable as bytes or bytes[].

Tips

For arrays, you can specify the delimiter used to seperate the values with the delimiter parameter.

Examples

Single Value

With environment variable BYTES_VALUE=0x7109709ECfa91a80626fF3989D68f67F5b1DD12D;

bytes memory key = "BYTES_VALUE";
bytes expected = hex"7109709ECfa91a80626fF3989D68f67F5b1DD12D";
bytes output = cheats.envBytes(key);
assertEq(output, expected);

Array

With environment variable BYTES_VALUE=0x7109709ECfa91a80626fF3989D68f67F5b1DD12D,0x00;

bytes memory key = "BYTES_VALUES";
bytes memory delimiter = ",";
bytes[] memory expected = new bytes[](2);
expected[0] = hex"7109709ECfa91a80626fF3989D68f67F5b1DD12D";
expected[1] = hex"00";
bytes[] memory output = cheats.envBytes(key, delimiter);
for (uint i = 0; i < expected.length; ++i) {
    assert(keccak256(abi.encodePacked((output[i]))) == keccak256(abi.encodePacked((expected[i]))));
}

`parseJson`

Signature

// Return the value(s) that correspond to 'key'
vm.parseJson(string memory json, string memory key)
// Return the entire json file
vm.parseJson(string memory json);

Description

These cheatcodes are used to parse JSON files in the form of strings. Usually, it's coupled with vm.readFile() which returns an entire file in the form of a string.

You can use stdJson from forge-std, as a helper library for better UX.

The cheatcode accepts either a key to search for a specific value in the JSON, or no key to return the entire JSON. It returns the value as an abi-encoded bytes array. That means that you will have to abi.decode() to the appropriate type for it to function properly, else it will revert.

JSONpath Key

parseJson uses a syntax called JSONpath to form arbitrary keys for arbitrary json files. The same syntax (or rather a dialect) is used by the tool jq.

To read more about the syntax, you can visit the README of the rust library that we use under the hood to implement the feature. That way you can be certain that you are using the correct dialect of jsonPath.

JSON Encoding Rules

We use the terms number, string, object, array, boolean as they are defined in the JSON spec.

Encoding Rules

Numbers >= 0 are encoded as uint256
Negative numbers are encoded as int256
A string that can be decoded into a type of H160 and starts with 0x is encoded as an address. In other words, if it can be decoded into an address, it's probably an address
A string that starts with 0x is encoded as bytes32 if it has a length of 66 or else to bytes
A string that is neither an address, a bytes32 or bytes, is encoded as a string
An array is encoded as a dynamic array of the type of its first element
An object ({}) is encoded as a tuple

Type Coercion

As described above, parseJSON needs to deduce the type of JSON value and that has some inherent limitations. For that reason, there is a sub-family of parseJson* cheatcodes that coerce the type of the returned value.

For example vm.parseJsonUint(json, key) will coerce the value to a uint256. That means that it can parse all the following values and return them as a uint256. That includes a number as type number, a stringified number as a string and of course it's hex representation.

{
  "hexUint": "0x12C980",
  "stringUint": "115792089237316195423570985008687907853269984665640564039457584007913129639935",
  "numberUint": 115792089237316195423570985008687907853269984665640564039457584007913129639935
}

Similarly, there are cheatcodes for all types (including bytes and bytes32) and their arrays (vm.parseJsonUintArray).

Decoding JSON objects into Solidity structs

JSON objects are encoded as tuples, and can be decoded via tuples or structs. That means that you can define a struct in Solidity and it will decode the entire JSON object into that struct.

For example:

The following JSON

{
  "a": 43,
  "b": "sigma"
}

will be decoded into:

struct Json {
    uint256 a;
    string b;
}

As the values are returned as an abi-encoded tuple, the exact name of the attributes of the struct don't need to match the names of the keys in the JSON. The above json file could also be decoded as:

struct Json {
    uint256 apple;
    string pineapple;
}

What matters is the alphabetical order. As the JSON object is an unordered data structure but the tuple is an ordered one, we had to somehow give order to the JSON. The easiest way was to order the keys by alphabetical order. That means that in order to decode the JSON object correctly, you will need to define attributes of the struct with types that correspond to the values of the alphabetical order of the keys of the JSON.

The struct is interpreted serially. That means that the tuple's first item will be decoded based on the first item of the struct definition (no alphabetical order).
The JSON will parsed alphabetically, not serially.

Thus, the first (in alphabetical order) value of the JSON, will be abi-encoded and then tried to be abi-decoded, based on the type of the first attribute of the struct.

The above JSON would not be able to be decoded with the struct below:

struct Json {
    uint256 b;
    uint256 a;
}

The reason is that it would try to decode the string "sigma" as a uint. To be exact, it would be decoded, but it would result to a wrong number, since it would interpret the bytes incorrectly.

Decoding JSON Objects, a tip

If your JSON object has hex numbers, they will be encoded as bytes. The way to decode them as uint for better UX, is to define two struct, one intermediary with the definition of these values as bytes and then a final struct that will be consumed by the user.

Decode the JSON into the intermediary struct
Convert the intermediary struct to the final one, by converting the bytes to uint. We have a helper function in forge-std to do this
Give the final struct to the user for consumption

How to use StdJson

Import the library import "../StdJson.sol";
Define its usage with string: using stdJson for string;
If you want to parse simple values (numbers, address, etc.) use the helper functions
If you want to parse entire JSON objects:
1. Define the struct in Solidity. Make sure to follow the alphabetical order -- it's hard to debug
2. Use the parseRaw() helper function to return abi-encoded bytes and then decode them to your struct

string memory root = vm.projectRoot();
string memory path = string.concat(root, "/src/test/fixtures/broadcast.log.json");
string memory json = vm.readFile(path);
bytes memory transactionDetails = json.parseRaw(".transactions[0].tx");
RawTx1559Detail memory rawTxDetail = abi.decode(transactionDetails, (RawTx1559Detail));

Forge script artifacts

We have gone ahead and created a handful of helper struct and functions to read the artifacts from broadcasting a forge script.

Currently, we only support artifacts produced by EIP1559-compatible chains and we don't support yet the parsing of the entire broadcast.json artifact. You will need to parse for individual values such as the transactions, the receipts, etc.

To read the transactions, it's as easy as doing:

function testReadEIP1559Transactions() public {
    string memory root = vm.projectRoot();
    string memory path = string.concat(root, "/src/test/fixtures/broadcast.log.json");
    Tx1559[] memory transactions = readTx1559s(path);
}

and then you can access their various fields in these structs:

struct Tx1559 {
    string[] arguments;
    address contractAddress;
    string contractName;
    string functionSig;
    bytes32 hash;
    Tx1559Detail txDetail;
    string opcode;
}

struct Tx1559Detail {
    AccessList[] accessList;
    bytes data;
    address from;
    uint256 gas;
    uint256 nonce;
    address to;
    uint256 txType;
    uint256 value;
}

References

Helper Library: stdJson.sol
Usage examples: stdCheats.t.sol
File Cheatcodes: cheatcodes for working with files

`serializeJson`

Signature

function serializeBool(string calldata objectKey, string calldata valueKey, bool value)
    external
    returns (string memory json);

function serializeUint(string calldata objectKey, string calldata valueKey, uint256 value)
    external
    returns (string memory json);

function serializeInt(string calldata objectKey, string calldata valueKey, int256 value)
    external
    returns (string memory json);

function serializeAddress(string calldata objectKey, string calldata valueKey, address value)
    external
    returns (string memory json);

function serializeBytes32(string calldata objectKey, string calldata valueKey, bytes32 value)
    external
    returns (string memory json);

function serializeString(string calldata objectKey, string calldata valueKey, string calldata value)
    external
    returns (string memory json);

function serializeBytes(string calldata objectKey, string calldata valueKey, bytes calldata value)
    external
    returns (string memory json);

function serializeBool(string calldata objectKey, string calldata valueKey, bool[] calldata values)
    external
    returns (string memory json);

function serializeUint(string calldata objectKey, string calldata valueKey, uint256[] calldata values)
    external
    returns (string memory json);

function serializeInt(string calldata objectKey, string calldata valueKey, int256[] calldata values)
    external
    returns (string memory json);

function serializeAddress(string calldata objectKey, string calldata valueKey, address[] calldata values)
    external
    returns (string memory json);

function serializeBytes32(string calldata objectKey, string calldata valueKey, bytes32[] calldata values)
    external
    returns (string memory json);

function serializeString(string calldata objectKey, string calldata valueKey, string[] calldata values)
    external
    returns (string memory json);

function serializeBytes(string calldata objectKey, string calldata valueKey, bytes[] calldata values)
    external
    returns (string memory json);

Description

Serializes values as a stringified JSON object.

How it works

The idea is that the user serializes the values of the JSON file and finally writes that object to a file. The user needs to pass:

A key for the object to which the value should be serialized to. This enables the user to serialize multiple objects in parallel
A key for the value which will be its key in the JSON file
The value to be serialized

The keys does not need to be of some specific form. They are of type string to enable for intuitive human interpretation. Semantically, they are not important other than to be used as keys.

The cheatcodes return the JSON object that is being serialized up to that point. That way the user can serialize inner JSON objects and then serialize them in bigger JSON objects, enabling the user to create arbitrary JSON objects.

Finally, the user writes the JSON object to a file by using writeJson.

Remember: The file path needs to be in the allowed paths. Read more in File cheatcodes.

Example

Let's assume we want to write the following JSON to a file:

{ "boolean": true, "number": 342, "object": { "title": "finally json serialization" } }

string memory obj1 = "some key";
vm.serializeBool(obj1, "boolean", true);
vm.serializeUint(obj1, "number", uint256(342));

string memory obj2 = "some other key";
string memory output = vm.serializeString(obj2, "title", "finally json serialization");

// IMPORTANT: This works because `serializeString` first tries to interpret `output` as
//   a stringified JSON object. If the parsing fails, then it treats it as a normal
//   string instead.
//   For instance, an `output` equal to '{ "ok": "asd" }' will produce an object, but
//   an output equal to '"ok": "asd" }' will just produce a normal string.
string memory finalJson = vm.serializeString(obj1, "object", output);

vm.writeJson(finalJson, "./output/example.json");

`writeJson`

Signature

function writeJson(string calldata json, string calldata path) external;

function writeJson(string calldata json, string calldata path, string calldata valueKey) external;

Description

Writes a serialized JSON object to a file.

The argument json must be a JSON object in stringified form. For example:

{ "boolean": true, "number": 342, "object": { "title": "finally json serialization" } }

This is usually built through serializeJson.

The argument path is the path of the JSON file to write to.

If no valueKey is provided, then the JSON object will be written to a new file. If the file already exists, it will be overwritten.

If a valueKey is provided, then the file must already exist and be a valid JSON file. The object in that file will be updated by replacing the value at the JSON path valueKey with the JSON object json.

This is useful to replace some values in a JSON file without having to first parse and then reserialize it. Note that the JSON path must indicate an existing key, so it's not possible to add new keys this way.

Remember: The file path path needs to be in the allowed paths. Read more in File cheatcodes.

JSON Paths

Let's consider the following JSON object:

{
  "boolean": true,
  "number": 342,
  "obj1": {
    "aNumber": 123,
    "obj2": {
      "aNumber": 123,
      "obj3": {
        "veryDeep": 13371337
      }
    }
  }
}

The root object is always assumed, so we can refer to one of its children by starting the path with a dot (.). For instance, .boolean, .number, and .obj1. We can go as deep as we want: .obj1.aNumber, or .obj1.obj2.aNumber. We can even search for a key in a subtree: .obj1..veryDeep, or just ..veryDeep since there's no ambiguity.

See the examples to see this in action.

Examples

A simple example

string memory jsonObj = '{ "boolean": true, "number": 342, "myObject": { "title": "finally json serialization" } }';
vm.writeJson(jsonObj, "./output/example.json");

// replaces the value of `myObject` with a new object
string memory newJsonObj = '{ "aNumber": 123, "aString": "asd" }';
vm.writeJson(newJsonObj, "./output/example.json", ".myObject");

// replaces the value of `aString` in the new object
vm.writeJson("my new string", "./output/example.json", ".myObject.aString");

// Here's example.json:
// 
// {
//   "boolean": true,
//   "number": 342,
//   "myObject": {
//     "aNumber": 123,
//     "aString": "my new string"
//   }
// }

A more complex example

string memory jsonObj = '{ "boolean": true, "number": 342, "obj1": { "foo": "bar" } }';
vm.writeJson(jsonObj, "./output/example2.json");

string memory jsonObj2 = '{ "aNumber": 123, "obj2": {} }';
vm.writeJson(jsonObj2, "./output/example2.json", ".obj1");

string memory jsonObj3 = '{ "aNumber": 123, "obj3": { "veryDeep": 3 } }';
vm.writeJson(jsonObj3, "./output/example2.json", ".obj1.obj2");

// Here's example2.json so far:
//
// {
//   "boolean": true,
//   "number": 342,
//   "obj1": {
//     "aNumber": 123,
//     "obj2": {
//       "aNumber": 123,
//       "obj3": {
//         "veryDeep": 3
//       }
//     }
//   }
// }

// Note that the JSON object is just the value 13371337 in this case.
vm.writeJson("13371337", "./output/example2.json", "..veryDeep");

// Here's the final example2.json:
//
// {
//   "boolean": true,
//   "number": 342,
//   "obj1": {
//     "aNumber": 123,
//     "obj2": {
//       "aNumber": 123,
//       "obj3": {
//         "veryDeep": 13371337
//       }
//     }
//   }
// }

Utilities

`addr`

Signature

function addr(uint256 privateKey) external returns (address);

Description

Computes the address for a given private key.

Examples

address alice = vm.addr(1);
emit log_address(alice); // 0x7e5f4552091a69125d5dfcb7b8c2659029395bdf

`sign`

Signature

function sign(uint256 privateKey, bytes32 digest) external returns (uint8 v, bytes32 r, bytes32 s);

Description

Signs a digest digest with private key privateKey, returning (v, r, s).

This is useful for testing functions that take signed data and perform an ecrecover to verify the signer.

Examples

address alice = vm.addr(1);
bytes32 hash = keccak256("Signed by Alice");
(uint8 v, bytes32 r, bytes32 s) = vm.sign(1, hash);
address signer = ecrecover(hash, v, r, s);
assertEq(alice, signer); // [PASS]

This is useful for testing functions that require a signature:

// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.8.17;

import { ECDSA } from "@openzeppelin/contracts/utils/cryptography/ECDSA.sol";

contract SigningExample is Ownable {
    using ECDSA for bytes32;

    address public systemAddress;

    function setSystemAddress(address _address) external onlyOwner {
        systemAddress = _address;
    }

    function purchase(uint256 _amount, string calldata _nonce, bytes calldata _signature) external payable {
        require(isValidSignature(
            systemAddress,
            keccak256(abi.encodePacked(msg.sender, _amount, _nonce)),
            _signature
            ), "Invalid Signature"
        );

        // mint tokens
    }

    function isValidSignature(address _systemAddress, bytes32 hash, bytes memory signature) internal view returns (bool) {
        require(_systemAddress != address(0), "Missing System Address");

        bytes32 signedHash = hash.toEthSignedMessageHash();
        return signedHash.recover(signature) == _systemAddress;
    }

}

contract SigningExampleTest is Test {
    using ECDSA for bytes32;

    SigningExample public signingExample;

    uint256 internal userPrivateKey;
    uint256 internal signerPrivateKey;

    function setUp() public {
        signingExample = new SigningExample();

        userPrivateKey = 0xa11ce;
        signerPrivateKey = 0xabc123;

        address signer = vm.addr(signerPrivateKey);
        signingExample.setSystemAddress(signer);
    }

    function testPurchase() public {
        address user = vm.addr(userPrivateKey);
        address signer = vm.addr(signerPrivateKey);

        uint256 amount = 2;
        string memory nonce = 'QSfd8gQE4WYzO29';

        vm.startPrank(signer);
        bytes32 digest = keccak256(abi.encodePacked(user, amount, nonce)).toEthSignedMessageHash();
        (uint8 v, bytes32 r, bytes32 s) = vm.sign(signerPrivateKey, digest);
        bytes memory signature = abi.encodePacked(r, s, v); // note the order here is different from line above.
        vm.stopPrank();

        vm.startPrank(user);
        // Give the user some ETH, just for good measure
        vm.deal(user, 1 ether);

        signingExample.purchase(
            amount,
            nonce,
            signature
        );
        vm.stopPrank();
    }
}

`skip`

Signature

function skip(bool skip) external;

Description

Marks a test as skipped, conditionally. It must be called at the top of the test to ensure it is skipped without any execution.

If skip is called with a false boolean, it will not skip the test.

Tests marked as skipped will appear with a [SKIPPED] label on the test runner and on the summary, to easily identify skipped tests.

Examples


function testSkip() public {
    cheats.skip(true);
    /// This revert will not be reached as this test will be skipped.
    revert("Should not reach this revert");
}

function testNotSkip() public {
    cheats.skip(false);
    /// This revert will be reached as this test will not be skipped, and the test will fail.
    revert("Should reach this revert");
}

`label`

Signature

function label(address addr, string calldata label) external;

Description

Sets a label label for addr in test traces.

If an address is labelled, the label will show up in test traces instead of the address.

`deriveKey`

Signature

function deriveKey(
  string calldata mnemonic,
  uint32 index
) external returns (uint256);

function deriveKey(
  string calldata mnemonic,
  string calldata path,
  uint32 index
) external returns (uint256);

Description

Derive a private key from a given mnemonic or mnemonic file path.

The first signature derives at the derivation path m/44'/60'/0'/0/{index}. The second signature allows you to specify the derivation path as the second parameter.

Examples

Derive the private key from the test mnemonic at path m/44'/60'/0'/0/0:

string memory mnemonic = "test test test test test test test test test test test junk";
uint256 privateKey = vm.deriveKey(mnemonic, 0);

Derive the private key from the test mnemonic at path m/44'/60'/0'/1/0:

string memory mnemonic = "test test test test test test test test test test test junk";
uint256 privateKey = vm.deriveKey(mnemonic, "m/44'/60'/0'/1/", 0);

`parseBytes`

Signature

function parseBytes(string calldata stringifiedValue) external pure returns (bytes memory parsedValue);

Description

Parses the value of string into bytes

Examples

string memory bytesAsString = "0x00000000000000000000000000000000";
bytes memory stringToBytes = vm.parseBytes(bytesAsString); // 0x00000000000000000000000000000000

`parseAddress`

Signature

function parseAddress(string calldata stringifiedValue) external pure returns (address parsedValue);

Description

Parses the value of string into address

Examples

string memory addressAsString = "0x0000000000000000000000000000000000000000";
address stringToAddress = vm.parseAddress(addressAsString); // 0x0000000000000000000000000000000000000000

`parseUint`

Signature

function parseUint(string calldata stringifiedValue) external pure returns (uint256 parsedValue);

Description

Parses the value of string into uint256

Examples

string memory uintAsString = "12345";
uint256 stringToUint = vm.parseUint(uintAsString); // 12345

`parseInt`

Signature

function parseInt(string calldata stringifiedValue) external pure returns (int256 parsedValue);

Description

Parses the value of string into int256

Examples

string memory intAsString = "-12345";
int256 stringToInt = vm.parseInt(intAsString); // -12345

`parseBytes32`

Signature

function parseBytes32(string calldata stringifiedValue) external pure returns (bytes32 parsedValue);

Description

Parses the value of string into bytes32

Examples

string memory bytes32AsString = "0x0000000000000000000000000000000000000000000000000000000000000000";
bytes32 stringToBytes32 = vm.parseBytes32(bytes32AsString); // 0x0000000000000000000000000000000000000000000000000000000000000000

`parseBool`

Signature

function parseBool(string calldata stringifiedValue) external pure returns (bool parsedValue);

Description

Parses the value of string into bool

Examples

string memory boolAsString = "false";
bool stringToBool = vm.parseBool(boolAsString); // false

`rememberKey`

Signature

function rememberKey(uint256 privateKey) external returns (address);

Description

Stores a private key in forge's local wallet and returns the corresponding address which can later be used for broadcasting.

Examples

Derive the private key from the test mnemonic at path m/44'/60'/0'/0/0, remember it in forge's wallet and use it to start broadcasting transactions:

string memory mnemonic = "test test test test test test test test test test test junk";
uint256 privateKey = vm.deriveKey(mnemonic, 0);
address deployer = vm.rememberKey(privateKey);

vm.startBroadcast(deployer);
...
vm.stopBroadcast();

Load a private key from the PRIVATE_KEY environment variable and use it to start broadcasting transactions:

address deployer = vm.rememberKey(vm.envUint("PRIVATE_KEY"));

vm.startBroadcast(deployer);
...
vm.stopBroadcast();

`toString`

Signature

function toString(address) external returns (string memory);
function toString(bool) external returns (string memory);
function toString(uint256) external returns (string memory);
function toString(int256) external returns (string memory);
function toString(bytes32) external returns (string memory);
function toString(bytes) external returns (string memory);

Description

Convert any type to its string version. Very useful for operations that demand strings, such as the cheatcode ffi.

Bytes are converted to a string of their hex representation with 0x at the start, signifying that they are encoded in hex.

Examples

uint256 number = 420;
string memory stringNumber = vm.toString(number);
vm.assertEq(stringNumber, "420");

bytes memory testBytes = hex"7109709ECfa91a80626fF3989D68f67F5b1DD12D";
string memory stringBytes = cheats.toString(testBytes);
assertEq("0x7109709ecfa91a80626ff3989d68f67f5b1dd12d", stringBytes);

address testAddress =  0x7109709ECfa91a80626fF3989D68f67F5b1DD12D;
string memory stringAddress = cheats.toString(testAddress);
assertEq("0x7109709ECfa91a80626fF3989D68f67F5b1DD12D", stringAddress);

`breakpoint`

Signature

function breakpoint(string) external;
function breakpoint(string, bool) external;

Description

Places a breakpoint to jump to in the debugger view.

Calling vm.breakpoint('<char>, true) is equivalent to vm.breakpoint('<char>), but calling vm.breakpoint('<char, false) will erase the breakpoint at '<char.

If the char is overwritten, only the last one that was visited in the execution steps is considered.

Examples

function testBreakpoint() public {
    vm.breakpoint("a");
}

Opening up the debugger in a test environment and pressing 'a will then place the debugger step at the place where the breakpoint cheatcode was called.

breakpoint a

snapshot cheatcodes

Signature

// Snapshot the current state of the evm.
// Returns the id of the snapshot that was created.
// To revert a snapshot use `revertTo`
function snapshot() external returns(uint256);
// Revert the state of the evm to a previous snapshot
// Takes the snapshot id to revert to.
// This deletes the snapshot and all snapshots taken after the given snapshot id.
function revertTo(uint256) external returns(bool);

Description

snapshot takes a snapshot of the state of the blockchain and returns the identifier of the created snapshot

revertTo reverts the state of the blockchain to the given snapshot. This deletes the given snapshot, as well as any snapshots taken after (e.g.: reverting to id 2 will delete snapshots with ids 2, 3, 4, etc.)

Examples

struct Storage {
    uint slot0;
    uint slot1;
}

contract SnapshotTest is Test {
    Storage store;
    uint256 timestamp;

    function setUp() public {
        store.slot0 = 10;
        store.slot1 = 20;
        vm.deal(address(this), 5 ether);        // balance = 5 ether
        timestamp = block.timestamp;
    }

    function testSnapshot() public {
        uint256 snapshot = vm.snapshot();       // saves the state

        // let's change the state
        store.slot0 = 300;
        store.slot1 = 400;
        vm.deal(address(this), 500 ether);
        vm.warp(12345);                         // block.timestamp = 12345

        assertEq(store.slot0, 300);
        assertEq(store.slot1, 400);
        assertEq(address(this).balance, 500 ether);
        assertEq(block.timestamp, 12345);

        vm.revertTo(snapshot);                  // restores the state

        assertEq(store.slot0, 10, "snapshot revert for slot 0 unsuccessful");
        assertEq(store.slot1, 20, "snapshot revert for slot 1 unsuccessful");
        assertEq(address(this).balance, 5 ether, "snapshot revert for balance unsuccessful");
        assertEq(block.timestamp, timestamp, "snapshot revert for timestamp unsuccessful");
    }
}

Signature

// Returns the URL for a configured alias
function rpcUrl(string calldata alias) external returns(string memory);
// Returns all configured (alias, URL) pairs
function rpcUrls() external returns(string[2][] memory);

Description

Provides cheatcodes to access all RPC endpoints configured in the rpc_endpoints object of the foundry.toml

Examples

The following rpc_endpoints in foundry.toml registers two RPC aliases:

optimism references the URL directly
mainnet references the RPC_MAINNET environment value that is expected to contain the actual URL

Env variables need to be wrapped in ${}

# --snip--
[rpc_endpoints]
optimism = "https://optimism.alchemyapi.io/v2/..."
mainnet = "${RPC_MAINNET}"

string memory url = vm.rpcUrl("optimism");
assertEq(url, "https://optimism.alchemyapi.io/v2/...");

If a ENV var is missing, rpcUrl() will revert:

vm.expectRevert("Failed to resolve env var `${RPC_MAINNET}` in `RPC_MAINNET`: environment variable not found");
string memory url = vm.rpcUrl("mainnet");

Retrieve all available alias -> URL pairs

string[2][] memory allUrls = vm.rpcUrls();
assertEq(allUrls.length, 2);

string[2] memory val = allUrls[0];
assertEq(val[0], "optimism");

string[2] memory env = allUrls[1];
assertEq(env[0], "mainnet");

File cheat codes

Signature

// Reads the entire content of file to string, (path) => (data)
function readFile(string calldata) external returns (string memory);
// Reads next line of file to string, (path) => (line)
function readLine(string calldata) external returns (string memory);
// Writes data to file, creating a file if it does not exist, and entirely replacing its contents if it does.
// (path, data) => ()
function writeFile(string calldata, string calldata) external;
// Writes line to file, creating a file if it does not exist.
// (path, data) => ()
function writeLine(string calldata, string calldata) external;
// Closes file for reading, resetting the offset and allowing to read it from beginning with readLine.
// (path) => ()
function closeFile(string calldata) external;
// Removes file. This cheatcode will revert in the following situations, but is not limited to just these cases:
// - Path points to a directory.
// - The file doesn't exist.
// - The user lacks permissions to remove the file.
// (path) => ()
function removeFile(string calldata) external;

Description

These cheatcodes provided by forge-std can be used for filesystem manipulation operations.

By default, filesystem access is disallowed and requires the fs_permission setting in foundry.toml:

# Configures permissions for cheatcodes that touch the filesystem like `vm.writeFile`
# `access` restricts how the `path` can be accessed via cheatcodes
#    `read-write` | `true`   => `read` + `write` access allowed (`vm.readFile` + `vm.writeFile`)
#    `none`| `false` => no access
#    `read` => only read access (`vm.readFile`)
#    `write` => only write access (`vm.writeFile`)
# The `allowed_paths` further lists the paths that are considered, e.g. `./` represents the project root directory
# By default _no_ fs access permission is granted, and _no_ paths are allowed
# following example enables read access for the project dir _only_:
#       `fs_permissions = [{ access = "read", path = "./"}]`
fs_permissions = [] # default: all file cheat codes are disabled

Examples

Append a line to a file, this will create the file if it does not exist yet

This requires read access to the file / project root

fs_permissions = [{ access = "read", path = "./"}]

string memory path = "output.txt";

string memory line1 = "first line";
vm.writeLine(path, line1);

string memory line2 = "second line";
vm.writeLine(path, line2);

Write to and read from a file

This requires read-write access to file / project root:

fs_permissions = [{ access = "read-write", path = "./"}]

string memory path = "file.txt";
string memory data = "hello world";
vm.writeFile(path, data);

assertEq(vm.readFile(path), data);

Remove a file

This requires write access to file / project root:

fs_permissions = [{ access = "write", path = "./"}]

string memory path = "file.txt";
string memory data = "hello world";
vm.writeFile(path, data);

assertEq(vm.readFile(path), data);

Forge Standard Library Reference

Forge Standard Library (Forge Std for short) is a collection of helpful contracts that make writing tests easier, faster, and more user-friendly.

Using Forge Std is the preferred way of writing tests with Foundry.

What's included:

Vm.sol: Up-to-date cheatcodes interface
```
import "forge-std/Vm.sol";
```
console.sol and console2.sol: Hardhat-style logging functionality
```
import "forge-std/console.sol";
```
Note: console2.sol contains patches to console.sol that allow Forge to decode traces for calls to the console, but it is not compatible with Hardhat.
```
import "forge-std/console2.sol";
```
Script.sol: Basic utilities for Solidity scripting
```
import "forge-std/Script.sol";
```
Test.sol: The complete Forge Std experience (more details below)
```
import "forge-std/Test.sol";
```

Forge Std's `Test`

The Test contract in Test.sol provides all the essential functionality you need to get started writing tests.

Simply import Test.sol and inherit from Test in your test contract:

import "forge-std/Test.sol";

contract ContractTest is Test { ...

What's included:

Std Libraries
- Std Logs: Expand upon the logging events from the DSTest library.
- Std Assertions: Expand upon the assertion functions from the DSTest library.
- Std Cheats: Wrappers around Forge cheatcodes for improved safety and DX.
- Std Errors: Wrappers around common internal Solidity errors and reverts.
- Std Storage: Utilities for storage manipulation.
- Std Math: Useful mathematical functions.
- Script Utils: Utility functions which can be accessed in tests and scripts.
- Console Logging: Console logging functions.
A cheatcodes instance vm, from which you invoke Forge cheatcodes (see Cheatcodes Reference)
```
vm.startPrank(alice);
```
All Hardhat console functions for logging (see Console Logging)
```
console.log(alice.balance); // or `console2`
```
All Dappsys Test functions for asserting and logging (see Dappsys Test reference)
```
assertEq(dai.balanceOf(alice), 10000e18);
```

Utility functions also included in Script.sol (see Script Utils)

// Compute the address a contract will be deployed at for a given deployer address and nonce
address futureContract = computeCreateAddress(alice, 1);

Std Logs

Std Logs expand upon the logging events from the DSTest library.

Events

event log_array(uint256[] val);
event log_array(int256[] val);
event log_named_array(string key, uint256[] val);
event log_named_array(string key, int256[] val);

Usage

This section provides usage examples.

log_array

event log_array(<type>[] val);

Where <type> can be int256, uint256, address.

Example

// Assuming storage
// uint256[] data = [10, 20, 30, 40, 50]; 

emit log_array(data);

log_named_array

event log_named_array(string key, <type>[] val);

Where <type> can be int256, uint256, address.

Example

// Assuming storage
// uint256[] data = [10, 20, 30, 40, 50]; 

emit log_named_array("Data", data);

Std Assertions

`fail`

Signature

function fail(string memory err) internal virtual;

Description

Fail a test with a message if a certain branch or execution point is hit.

Examples

function test() external {
    for(uint256 place; place < 10; ++i){
        if(game.leaderboard(place) == address(this)) return;
    }
    fail("Not in the top 10.");
}

`assertFalse`

Signature

function assertFalse(bool data) internal virtual;

function assertFalse(bool data, string memory err) internal virtual;

Description

Asserts the condition is false.

Examples

bool failure = contract.fun();
assertFalse(failure);

`assertEq`

Signature

function assertEq(bool a, bool b) internal;

function assertEq(bool a, bool b, string memory err) internal;

function assertEq(bytes memory a, bytes memory b) internal;

function assertEq(bytes memory a, bytes memory b, string memory err) internal;

function assertEq(uint256[] memory a, uint256[] memory b) internal;

function assertEq(int256[] memory a, int256[] memory b) internal;

function assertEq(uint256[] memory a, uint256[] memory b, string memory err) internal;

function assertEq(int256[] memory a, int256[] memory b, string memory err) internal;

// legacy helper for asserting two uints shorter than 256 bits: `assertEqUint(uint8(1), uint128(1));`
function assertEqUint(uint256 a, uint256 b) internal;

Description

Asserts a is equal to b.

Works with bool, bytes, and int256 and uint256 arrays.

`assertApproxEqAbs`

Signature

function assertApproxEqAbs(uint256 a, uint256 b, uint256 maxDelta) internal virtual;

function assertApproxEqAbs(uint256 a, uint256 b, uint256 maxDelta, string memory err) internal virtual;

Description

Asserts a is approximately equal to b with delta in absolute value.

Examples

function testFail () external {
    uint256 a = 100;
    uint256 b = 200;

    assertApproxEqAbs(a, b, 90);
}

[PASS] testFail() (gas: 23169)
Logs:
  Error: a ~= b not satisfied [uint]
    Expected: 200
      Actual: 100
   Max Delta: 90
       Delta: 100

`assertApproxEqRel`

Signature

function assertApproxEqRel(uint256 a, uint256 b, uint256 maxPercentDelta) internal virtual;

function assertApproxEqRel(uint256 a, uint256 b, uint256 maxPercentDelta, string memory err) internal virtual;

Description

Asserts a is approximately equal to b with delta in percentage, where 1e18 is 100%.

Examples

function testFail () external {
    uint256 a = 100;
    uint256 b = 200;
    assertApproxEqRel(a, b, 0.4e18);
}

[PASS] testFail() (gas: 23884)
Logs:
  Error: a ~= b not satisfied [uint]
      Expected: 200
        Actual: 100
   Max % Delta: 0.400000000000000000
       % Delta: 0.500000000000000000

Std Cheats

`skip`

Signature

function skip(uint256 time) public;

Description

Skips forward block.timestamp by the specified number of seconds.

Examples

assertEq(block.timestamp, 0);
skip(3600);
assertEq(block.timestamp, 3600);

`rewind`

Signature

function rewind(uint256 time) public;

Description

Rewinds block.timestamp by the specified number of seconds.

Examples

assertEq(block.timestamp, 3600);
rewind(3600);
assertEq(block.timestamp, 0);

`hoax`

Signature

function hoax(address who) public;

function hoax(address who, uint256 give) public;

function hoax(address who, address origin) public;

function hoax(address who, address origin, uint256 give) public;

Description

Sets up a prank from an address that has some ether.

If the balance is not specified, it will be set to 2^128 wei.

`startHoax`

Signature

function startHoax(address who) public;

function startHoax(address who, uint256 give) public;

function startHoax(address who, address origin) public;

function startHoax(address who, address origin, uint256 give) public;

Description

Start a perpetual prank from an address that has some ether.

If the balance is not specified, it will be set to 2^128 wei.

`deal`

Signature

function deal(address to, uint256 give) public;

function deal(address token, address to, uint256 give) public;

function deal(address token, address to, uint256 give, bool adjust) public;

Description

A wrapper around the deal cheatcode that also works for most ERC-20 tokens.

If the alternative signature of deal is used, adjusts the token's total supply after setting the balance.

Examples

deal(address(dai), alice, 10000e18);
assertEq(dai.balanceOf(alice), 10000e18);

`deployCode`

Signature

function deployCode(string memory what) public returns (address);

function deployCode(string memory what, bytes memory args) public returns (address);

function deployCode(string memory what, uint256 val) public returns (address);

function deployCode(string memory what, bytes memory args, uint256 val) public returns (address);

Description

Deploys a contract by fetching the contract bytecode from the artifacts directory.

Values can also be passed by using the val parameter. This is necessary if you need to send ETH on construction.

Examples

address deployment = deployCode("MyContract.sol", abi.encode(arg1, arg2));

`deployCodeTo`

Signature

function deployCodeTo(string memory what, address where) internal virtual;

function deployCodeTo(string memory what, bytes memory args, address where) internal virtual;

function deployCodeTo(string memory what, bytes memory args, uint256 value, address where) internal virtual;

Description

Pseudo-deploys a contract to an arbitrary address by fetching the contract bytecode from the artifacts directory. This can be used to recreate the production environment.

Values can also be passed by using the vaue parameter. This is necessary if you need to send ETH on construction.

Examples

deployCodeTo("MyContract.sol", abi.encode(arg1, arg2), arbitraryAddr);

`bound`

Signature

function bound(uint256 x, uint256 min, uint256 max) public returns (uint256 result);

Description

A mathematical function for wrapping inputs of fuzz tests into a certain range.

You can use it instead of the assume cheatcode to get better performance in some cases. Read more here.

Examples

input = bound(input, 99, 101);

Returns 99 for input 0.
Returns 100 for input 1.
Returns 101 for input 2.
Returns 99 for input 3.
And so on.

`changePrank`

Signature

function changePrank(address who) internal;

Description

Stops the active prank with stopPrank and passes address to startPrank.

Useful for starting a global prank in the setUp function and deactivating it in certain tests.

`makeAddr`

Signature

function makeAddr(string memory name) internal returns(address addr);

Description

Creates an address derived from the provided name.

A label is created for the derived address with the provided name used as the label value.

Examples

address alice = makeAddr("alice");
emit log_address(alice); // 0x328809bc894f92807417d2dad6b7c998c1afdac6

`makeAddrAndKey`

Signature

function makeAddrAndKey(string memory name) internal returns(address addr, uint256 privateKey);

Description

Creates an address and private key derived from the provided name.

A label is created for the derived address with the provided name used as the label value.

Examples

(address alice, uint256 key) = makeAddrAndKey("alice");
emit log_address(alice); // 0x328809bc894f92807417d2dad6b7c998c1afdac6
emit log_uint(key); // 70564938991660933374592024341600875602376452319261984317470407481576058979585

`noGasMetering`

Signature

modifier noGasMetering();

Description

A function modifier that turns off gas metering for the life of the function.

Note, there is some gas associated with calling the cheatcode, so you will see some gas usage (albeit small) when using this modifier.

Examples

function addInLoop() internal returns (uint256) {
    uint256 b;
    for (uint256 i; i < 10000; i++) {
        b + i;
    }
    return b;
}

function addInLoopNoGas() internal noGasMetering returns (uint256) {
    return addInLoop();
}

function testFunc() external {
  uint256 gas_start = gasleft();
  addInLoop();
  uint256 gas_used = gas_start - gasleft();

  uint256 gas_start_no_metering = gasleft();
  addInLoopNoGas();
  uint256 gas_used_no_metering = gas_start_no_metering - gasleft();

  emit log_named_uint("Gas Metering", gas_used);
  emit log_named_uint("No Gas Metering", gas_used_no_metering);
}

[PASS] testFunc() (gas: 1887191)
Logs:
  Gas Metering: 1880082
  No Gas Metering: 3024

`assumeNoPrecompiles`

Signature

function assumeNoPrecompiles(address addr) public;

function assumeNoPrecompiles(address addr, uint256 chainid) public;

Description

Uses assume to filter precompile addresses from the fuzz tests.

Optionally, a chainid may be specified to filter known precompiles on the respective chain.

`assumePayable`

Signature

function assumePayable(address addr) public;

Description

Uses assume to filter addresses that reject Ether transfers.

This makes an external call to the specified addr with a no calldata and checks assume against the success of the call.

Std Errors

`assertionError`

Signature

stdError.assertionError

Description

The internal Solidity error when an assert fails.

`arithmeticError`

Signature

stdError.arithmeticError

Description

The internal Solidity error when an arithmetic operation fails, e.g. underflow and overflow.

Example

Assume we have a basic vault contract that can store some token (wmdToken):

contract BasicVault {

    IERC20 public immutable wmdToken;   
    mapping(address => uint) public balances;

    event Deposited(address indexed from, uint amount);
    event Withdrawal(address indexed from, uint amount);

    constructor(IERC20 wmdToken_){
        wmdToken = wmdToken_;
    }

    function deposit(uint amount) external {    
        balances[msg.sender] += amount;
        bool success = wmdToken.transferFrom(msg.sender, address(this), amount);
        require(success, "Deposit failed!"); 
        emit Deposited(msg.sender, amount);
    }

    function withdraw(uint amount) external {      
        balances[msg.sender] -= amount;
        bool success = wmdToken.transfer(msg.sender, amount);
        require(success, "Withdrawal failed!");
        emit Withdrawal(msg.sender, amount);
    }
}

We have a test function to ensure that a user is unable to withdraw tokens in excess of his deposit, like so:

function testUserCannotWithdrawExcessOfDeposit() public {
    vm.prank(user);
    vm.expectRevert(stdError.arithmeticError);
    vault.withdraw(userTokens + 100*10**18);
}

User has tokens of amount userTokens deposited in a Vault contract.
User attempts to withdraw tokens of amount in excess of his deposits.
This leads to an underflow error, resulting from: balances[msg.sender] -= amount; as it would evaluate into a negative value.

To catch the error "Arithmetic over/underflow", we insert vm.expectRevert(stdError.arithmeticError) just before the function call that is expected to result in an underflow.

`divisionError`

Signature

stdError.divisionError

Description

The internal Solidity error when a division fails, e.g. division by zero.

`enumConversionError`

Signature

stdError.enumConversionError

Description

The internal Solidity error when trying to convert a number to a variant of an enum, if the number is larger than the number of variants in the enum (counting from 0).

`encodeStorageError`

Signature

stdError.encodeStorageError

Description

The internal Solidity error when trying to access data in storage that is corrupted. Data cannot be corrupted unless assembly had been used.

`popError`

Signature

stdError.popError

Description

The internal Solidity error when trying to pop an element off of an empty array.

`indexOOBError`

Signature

stdError.indexOOBError

Description

The internal Solidity error when trying to access an element of an array that is out of bounds.

Will not work for empty arrays in external contracts. For those, use expectRevert without any arguments.

`memOverflowError`

Signature

stdError.memOverflowError

Description

The internal Solidity error when trying to allocate a dynamic memory array with more than 2^64-1 items.

`zeroVarError`

Signature

stdError.zeroVarError

Description

The internal Solidity error when trying to call a function via a function pointer that has not been initialized.

Std Storage

Std Storage is a library that makes manipulating storage easy.

To use Std Storage, add the following line to your test contract:

using stdStorage for StdStorage;

Then, access Std Storage via the stdstore instance.

Functions

Query functions:

target: Set the address of the target contract
sig: Set the 4-byte selector of the function to static call
with_key: Pass an argument to the function (can be used multiple times)
depth: Set the position of the value in the tuple (e.g. inside a struct)

Terminator functions:

find: Return the slot number
checked_write: Set the data to be written to the storage slot(s)
read_<type>: Read the value from the storage slot as <type>

Example

playerToCharacter tracks info about players' characters.

// MetaRPG.sol

struct Character {
    string name;
    uint256 level;
}

mapping (address => Character) public playerToCharacter;

Let's say we want to set the level of our character to 120.

// MetaRPG.t.sol

stdstore
    .target(address(metaRpg))
    .sig("playerToCharacter(address)")
    .with_key(address(this))
    .depth(1)
    .checked_write(120);

Limitations

Accessing packed slots is not supported

Known issues

Slot(s) may not be found if the tuple contains types shorter than 32 bytes

`target`

Signature

function target(StdStorage storage self, address _target) internal returns (StdStorage storage);

Description

Sets the address of the contract.

Default value: address(0)

`sig`

Signature

function sig(StdStorage storage self, bytes4 _sig) internal returns (StdStorage storage);

function sig(StdStorage storage self, string memory _sig) internal returns (StdStorage storage);

Description

Sets the 4-byte selector of the function to static call.

Default value: hex"00000000"

Examples

uint256 slot = stdstore
    .target(addr)
    .sig(addr.fun.selector)
    .with_key(1)
    .find();

uint256 slot = stdstore
    .target(addr)
    .sig("fun(uint256)")
    .with_key(1)
    .find();

`with_key`

Signature

function with_key(StdStorage storage self, address who) internal returns (StdStorage storage);

function with_key(StdStorage storage self, uint256 amt) internal returns (StdStorage storage);

function with_key(StdStorage storage self, bytes32 key) internal returns (StdStorage storage);

Description

Passes an argument to the function.

Can be used multiple times to pass multiple arguments. The order matters.

Examples

uint256 slot = stdstore
    .target(addr)
    .sig("fun(uint256,address)")
    .with_key(1)
    .with_key(address(this))
    .find();

`depth`

Signature

function depth(StdStorage storage self, uint256 _depth) internal returns (StdStorage storage);

Description

Sets the position of the value in the tuple (e.g. inside a struct).

Default value: uint256(0)

`checked_write`

Signature

function checked_write(StdStorage storage self, address who) internal;

function checked_write(StdStorage storage self, uint256 amt) internal;

function checked_write(StdStorage storage self, bool write) internal;

function checked_write(StdStorage storage self, bytes32 set) internal;

Description

Sets the data to be written to the storage slot(s).

Reverts with a message if unsuccessful.

`find`

Signature

function find(StdStorage storage self) internal returns (uint256);

Description

Finds an arbitrary storage slot given target, sig, with_key(s), and depth.

Reverts with a message if unsuccessful.

`read`

Signature

function read_bytes32(StdStorage storage self) internal returns (bytes32);

function read_bool(StdStorage storage self) internal returns (bool);

function read_address(StdStorage storage self) internal returns (address);

function read_uint(StdStorage storage self) internal returns (uint256);

function read_int(StdStorage storage self) internal returns (int256);

Description

Reads the value from the storage slot as bytes32, bool, address, uint256, or int256.

Reverts with a message if unsuccessful.

Std Math

`abs`

Signature

function abs(int256 a) internal pure returns (uint256)

Description

Returns the absolute value of a number.

Example

uint256 ten = stdMath.abs(-10);

`delta`

Signature

function delta(uint256 a, uint256 b) internal pure returns (uint256)

function delta(int256 a, int256 b) internal pure returns (uint256)

Description

Returns the difference between two numbers in absolute value.

Example

uint256 four = stdMath.delta(-1, 3);

`percentDelta`

Signature

function percentDelta(uint256 a, uint256 b) internal pure returns (uint256)

function percentDelta(int256 a, int256 b) internal pure returns (uint256)

Description

Returns the difference between two numbers in percentage, where 1e18 is 100%. More precisely, percentDelta(a, b) computes abs((a-b) / b) * 1e18.

Example

uint256 percent150 = stdMath.percentDelta(uint256(125), 50);
uint256 percent60 = stdMath.percentDelta(uint256(50), 125);

Script Utils

`computeCreateAddress`

Signature

function computeCreateAddress(address deployer, uint256 nonce) internal pure returns (address)

Description

Compute the address a contract will be deployed at for a given deployer address and nonce. Useful to precalculate the address a contract will be deployed at.

Example

address governanceAddress = computeCreateAddress(0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266, 1);

// this contract requires a governance contract which hasn't been deployed yet
Contract contract = new Contract(governanceAddress);
// now we deploy it
Governance governance = new Governance(contract);

// assuming `contract` has a `governance()` accessor
assertEq(governanceAddress, address(governance)); // [PASS]

`deriveRememberKey`

Signature

function deriveRememberKey(string memory mnemonic, uint32 index) internal returns (address who, uint256 privateKey)

Description

Derive a private key from a mnemonic and also store it in forge's local wallet. Returns the address and private key.

Example

Get a private key and address from the test mnemonic at path m/44'/60'/0'/0/0. Use them to sign some data and start broadcasting transactions:

string memory mnemonic = "test test test test test test test test test test test junk";

(address deployer, uint256 privateKey) = deriveRememberKey(mnemonic, 0);

bytes32 hash = keccak256("Signed by deployer");
(uint8 v, bytes32 r, bytes32 s) = vm.sign(privateKey, hash);

vm.startBroadcast(deployer);
...
vm.stopBroadcast();

Get an address from the test mnemonic at path m/44'/60'/0'/0/0 to start broadcasting transactions:

string memory mnemonic = "test test test test test test test test test test test junk";

(address deployer, ) = deriveRememberKey(mnemonic, 0);

vm.startBroadcast(deployer);
...
vm.stopBroadcast();

Console Logging

Similar to Hardhat's console functions.
You can use it in calls and transactions. It works with view functions, but not in pure ones.
It always works, regardless of the call or transaction failing or being successful.
To use it you need to import forge-std/src/console.sol.
You can call console.log with up to 4 parameters in any order of following types:
- uint
- string
- bool
- address
There's also the single parameter API for the types above, and additionally bytes, bytes1... up to bytes32:
- console.logInt(int i)
- console.logUint(uint i)
- console.logString(string memory s)
- console.logBool(bool b)
- console.logAddress(address a)
- console.logBytes(bytes memory b)
- console.logBytes1(bytes1 b)
- console.logBytes2(bytes2 b)
- ...
- console.logBytes32(bytes32 b)
console.log implements the same formatting options that can be found in Hardhat's console.log.
- Example: console.log("Changing owner from %s to %s", currentOwner, newOwner)
console.log is implemented in standard Solidity and it is compatible Anvil and Hardhat Networks.
console.log calls can run in other networks, like mainnet, kovan, ropsten, etc. They do nothing in those networks, but do spend a minimal amount of gas.

`console.log(format[,...args])`

The console.log() method prints a formatted string using the first argument as a printf-like format string which can contain zero or more format specifiers. Each specifier is replaced with the converted value from the corresponding argument. Supported specifiers are:

%s: String will be used to convert all values to a human-readable string. uint256, int256 and bytes values are converted to their 0x hex encoded values.
%d: Number will be used to convert all values to a human-readable string. This is identical to %s.
%i: Works the same way as %d.
%e: The exponential representation of a number. For uint256 and int256 types.
%x: The hexadecimal representation of a number. For uint256 and int256 types.
%o: Object. A string representation of an object with generic JavaScript-styled object formatting. For solidity types, this basically surround the string representation of the value in single-quotes.
%%: single percent sign ('%'). This does not consume an argument.
Returns: <string> The formatted string

If a specifier does not have a corresponding argument, it is not replaced:

console.log("%s:%s", "foo");
// Returns: "foo:%s"

Values that are not part of the format string are formatted using as a human-readable string representation.

If there are more arguments passed to the console.log() method than the number of specifiers, the extra arguments are concatenated to the returned string, separated by spaces:

console.log("%s:%s", "foo", "bar", "baz");
// Returns: "foo:bar baz"

If only one argument is passed to console.log(), it is returned as it is without any formatting:

console.log("%% %s");
// Returns: "%% %s"

The String format specifier (%s) should be used in most cases unless specific functionality is needed from other format specifiers.

DSTest Reference

Dappsys Test (DSTest for short) provides basic logging and assertion functionality. It is included in the Forge Standard Library.

To get access to the functions, import forge-std/Test.sol and inherit from Test in your test contract:

import "forge-std/Test.sol";

contract ContractTest is Test {
    // ... tests ...
}

Logging

This is a complete overview of all the available logging events. For detailed descriptions and example usage, see below.

event log                    (string);
event logs                   (bytes);

event log_address            (address);
event log_bytes32            (bytes32);
event log_int                (int);
event log_uint               (uint);
event log_bytes              (bytes);
event log_string             (string);

event log_named_address      (string key, address val);
event log_named_bytes32      (string key, bytes32 val);
event log_named_decimal_int  (string key, int val, uint decimals);
event log_named_decimal_uint (string key, uint val, uint decimals);
event log_named_int          (string key, int val);
event log_named_uint         (string key, uint val);
event log_named_bytes        (string key, bytes val);
event log_named_string       (string key, string val);

Logging events

This section documents all events for logging and provides usage examples.

`log`

event log(string);

Example

emit log("here");
// here

logs

event logs(bytes);

Example

emit logs(bytes("abcd"));
// 0x6162636400000000000000000000000000000000000000000000000000000000

log_<type>

event log_<type>(<type>);

Where <type> can be address, bytes32, int, uint, bytes, string

Example

uint256 amount = 1 ether;
emit log_uint(amount);
// 1000000000000000000

log_named_<type>

event log_named_<type>(string key, <type> val);

Where <type> can be address, bytes32, int, uint, bytes, string

Example

uint256 amount = 1 ether;
emit log_named_uint("Amount", amount);
// amount: 1000000000000000000

log_named_decimal_<type>

event log_named_decimal_<type>(string key, <type> val, uint decimals);

Where <type> can be int, uint

Example

uint256 amount = 1 ether;
emit log_named_decimal_uint("Amount", amount, 18);
// amount: 1.000000000000000000

Asserting

This is a complete overview of all the available assertion functions. For detailed descriptions and example usage, see below.

// Assert the `condition` is true
function assertTrue(bool condition) internal;
function assertTrue(bool condition, string memory err) internal;

// Assert `a` is equal to `b`
function assertEq(address a, address b) internal;
function assertEq(address a, address b, string memory err) internal;
function assertEq(bytes32 a, bytes32 b) internal;
function assertEq(bytes32 a, bytes32 b, string memory err) internal;
function assertEq(int a, int b) internal;
function assertEq(int a, int b, string memory err) internal;
function assertEq(uint a, uint b) internal;
function assertEq(uint a, uint b, string memory err) internal;
function assertEqDecimal(int a, int b, uint decimals) internal;
function assertEqDecimal(int a, int b, uint decimals, string memory err) internal;
function assertEqDecimal(uint a, uint b, uint decimals) internal;
function assertEqDecimal(uint a, uint b, uint decimals, string memory err) internal;
function assertEq(string memory a, string memory b) internal;
function assertEq(string memory a, string memory b, string memory err) internal;
function assertEq32(bytes32 a, bytes32 b) internal;
function assertEq32(bytes32 a, bytes32 b, string memory err) internal;
function assertEq0(bytes memory a, bytes memory b) internal;
function assertEq0(bytes memory a, bytes memory b, string memory err) internal;

// Assert  `a` is greater than `b`
function assertGt(uint a, uint b) internal;
function assertGt(uint a, uint b, string memory err) internal;
function assertGt(int a, int b) internal;
function assertGt(int a, int b, string memory err) internal;
function assertGtDecimal(int a, int b, uint decimals) internal;
function assertGtDecimal(int a, int b, uint decimals, string memory err) internal;
function assertGtDecimal(uint a, uint b, uint decimals) internal;
function assertGtDecimal(uint a, uint b, uint decimals, string memory err) internal;

// Assert  `a` is greater than or equal to `b`
function assertGe(uint a, uint b) internal;
function assertGe(uint a, uint b, string memory err) internal;
function assertGe(int a, int b) internal;
function assertGe(int a, int b, string memory err) internal;
function assertGeDecimal(int a, int b, uint decimals) internal;
function assertGeDecimal(int a, int b, uint decimals, string memory err) internal;
function assertGeDecimal(uint a, uint b, uint decimals) internal;
function assertGeDecimal(uint a, uint b, uint decimals, string memory err) internal;

// Assert  `a` is lesser than `b`
function assertLt(uint a, uint b) internal;
function assertLt(uint a, uint b, string memory err) internal;
function assertLt(int a, int b) internal;
function assertLt(int a, int b, string memory err) internal;
function assertLtDecimal(int a, int b, uint decimals) internal;
function assertLtDecimal(int a, int b, uint decimals, string memory err) internal;
function assertLtDecimal(uint a, uint b, uint decimals) internal;
function assertLtDecimal(uint a, uint b, uint decimals, string memory err) internal;

// Assert  `a` is lesser than or equal to `b`
function assertLe(uint a, uint b) internal;
function assertLe(uint a, uint b, string memory err) internal;
function assertLe(int a, int b) internal;
function assertLe(int a, int b, string memory err) internal;
function assertLeDecimal(int a, int b, uint decimals) internal;
function assertLeDecimal(int a, int b, uint decimals, string memory err) internal;
function assertLeDecimal(uint a, uint b, uint decimals) internal;
function assertLeDecimal(uint a, uint b, uint decimals, string memory err) internal;

Assertion functions

This section documents all functions for asserting and provides usage examples.

`assertTrue`

function assertTrue(bool condition) internal;

Asserts the condition is true.

Example

bool success = contract.fun();
assertTrue(success);

`assertEq`

function assertEq(<type> a, <type> b) internal;

Where <type> can be address, bytes32, int, uint

Asserts a is equal to b.

Example

uint256 a = 1 ether;
uint256 b = 1e18 wei;
assertEq(a, b);

`assertEqDecimal`

function assertEqDecimal(<type> a, <type> b, uint decimals) internal;

Where <type> can be int, uint

Asserts a is equal to b.

Example

uint256 a = 1 ether;
uint256 b = 1e18 wei;
assertEqDecimal(a, b, 18);

`assertEq32`

function assertEq32(bytes32 a, bytes32 b) internal;

Asserts a is equal to b.

Example

assertEq(bytes32("abcd"), 0x6162636400000000000000000000000000000000000000000000000000000000);

`assertEq0`

function assertEq0(bytes a, bytes b) internal;

Asserts a is equal to b.

Example

string memory name1 = "Alice";
string memory name2 = "Bob";
assertEq0(bytes(name1), bytes(name2)); // [FAIL]

`assertGt`

function assertGt(<type> a, <type> b) internal;

Where <type> can be int, uint

Asserts a is greater than b.

Example

uint256 a = 2 ether;
uint256 b = 1e18 wei;
assertGt(a, b);

`assertGtDecimal`

function assertGtDecimal(<type> a, <type> b, uint decimals) internal;

Where <type> can be int, uint

Asserts a is greater than b.

Example

uint256 a = 2 ether;
uint256 b = 1e18 wei;
assertGtDecimal(a, b, 18);

`assertGe`

function assertGe(<type> a, <type> b) internal;

Where <type> can be int, uint

Asserts a is greater than or equal to b.

Example

uint256 a = 1 ether;
uint256 b = 1e18 wei;
assertGe(a, b);

`assertGeDecimal`

function assertGeDecimal(<type> a, <type> b, uint decimals) internal;

Where <type> can be int, uint

Asserts a is greater than or equal to b.

Example

uint256 a = 1 ether;
uint256 b = 1e18 wei;
assertGeDecimal(a, b, 18);

`assertLt`

function assertLt(<type> a, <type> b) internal;

Where <type> can be int, uint

Asserts a is lesser than b.

Example

uint256 a = 1 ether;
uint256 b = 2e18 wei;
assertLt(a, b);

`assertLtDecimal`

function assertLtDecimal(<type> a, <type> b, uint decimals) internal;

Where <type> can be int, uint

Asserts a is lesser than b.

Example

uint256 a = 1 ether;
uint256 b = 2e18 wei;
assertLtDecimal(a, b, 18);

`assertLe`

function assertLe(<type> a, <type> b) internal;

Where <type> can be int, uint

Asserts a is lesser than or equal to b.

Example

uint256 a = 1 ether;
uint256 b = 1e18 wei;
assertLe(a, b);

`assertLeDecimal`

function assertLeDecimal(<type> a, <type> b, uint decimals) internal;

Where <type> can be int, uint

Asserts a is lesser than or equal to b.

Example

uint256 a = 1 ether;
uint256 b = 1e18 wei;
assertLeDecimal(a, b, 18);

ℹ️ Information

You can pass a custom error message to the above functions by providing an additional parameter string err.

Miscellaneous

Struct Encoding

Structs are user defined types that can group several variables:

struct MyStruct {
    address addr;
    uint256 amount;
}

Only the new ABI coder v2 can encode and decode arbitrarily nested arrays and structs. Since Solidity 0.8.0 it is activated by default, prior to that it needs to be activated via pragma experimental ABIEncoderV2.

Solidity structs map to the ABI type "tuple". For more information on how Solidity types map to ABI types see Mapping Solidity to ABI types in the Solidity documentation.

Structs are therefore encoded and decoded as tuples. So the struct we defined above, MyStruct, maps to the tuple (address,uint256) in terms of the ABI.

Let's see how this works in a contract:

pragma solidity =0.8.15;


contract Test {
    struct MyStruct {
        address addr;
        uint256 amount;
    }
    function f(MyStruct memory t) public pure {}
}

The ABI of the f function in this contract is:

{
	"inputs": [
		{
			"components": [
				{
					"internalType": "address",
					"name": "addr",
					"type": "address"
				},
				{
					"internalType": "uint256",
					"name": "amount",
					"type": "uint256"
				}
			],
			"internalType": "struct Test.MyStruct",
			"name": "t",
			"type": "tuple"
		}
	],
	"name": "f",
	"outputs": [],
	"stateMutability": "pure",
	"type": "function"
}

which reads: The function f takes 1 input of type tuple with two components of type address and uint256.

Precompile Registry

Precompiles are special contracts at fixed addresses that are included within the EVM. In addition to common precompiles included with other EVM environments, Foundry includes a few precompiles for environment mutation, logging data, and contract deployment.

Note that, while some chains like Optimism have bytecode deployed at a predetermined address, making them 'pre-deploys', we treat them as precompiles within the context of Foundry.

Registry

Chain ID	Address	Name
ALL	`0x01`	ECRecover
ALL	`0x02`	SHA-256
ALL	`0x03`	RIPEMD-160
ALL	`0x04`	Identity
ALL	`0x05`	ModExp
ALL	`0x06`	ECAdd
ALL	`0x07`	ECMul
ALL	`0x08`	ECPairing
ALL	`0x09`	Blake2F
10, 420	`0x4200000000000000000000000000000000000016`	L2ToL1MessagePasser
10, 420	`0x4200000000000000000000000000000000000002`	DeployerWhitelist
10, 420	`0xDeadDeAddeAddEAddeadDEaDDEAdDeaDDeAD0000`	LegacyERC20ETH
10, 420	`0x4200000000000000000000000000000000000006`	WETH9
10, 420	`0x4200000000000000000000000000000000000007`	L2CrossDomainMessenger
10, 420	`0x4200000000000000000000000000000000000010`	L2StandardBridge
10, 420	`0x4200000000000000000000000000000000000011`	SequencerFeeVault
10, 420	`0x4200000000000000000000000000000000000012`	OptimismMintableERC20Factory
10, 420	`0x4200000000000000000000000000000000000013`	L1BlockNumber
10, 420	`0x420000000000000000000000000000000000000F`	GasPriceOracle
10, 420	`0x4200000000000000000000000000000000000015`	L1Block
10, 420	`0x4200000000000000000000000000000000000042`	GovernanceToken
10, 420	`0x4200000000000000000000000000000000000000`	LegacyMessagePasser
10, 420	`0x4200000000000000000000000000000000000014`	L2ERC721Bridge
10, 420	`0x4200000000000000000000000000000000000017`	OptimismMintableERC721Factory
10, 420	`0x4200000000000000000000000000000000000018`	ProxyAdmin
42161, 421613	`0x0000000000000000000000000000000000000064`	ArbSys
42161, 421613	`0x000000000000000000000000000000000000006E`	ArbRetryableTx
42161, 421613	`0x000000000000000000000000000000000000006C`	ArbGasInfo
42161, 421613	`0x0000000000000000000000000000000000000066`	ArbAddressTable
42161, 421613	`0x000000000000000000000000000000000000006F`	ArbStatistics
42161, 421613	`0x00000000000000000000000000000000000000C8`	NodeInterface
42161, 421613	`0x0000000000000000000000000000000000000067`	ArbBLS
42161, 421613	`0x0000000000000000000000000000000000000065`	ArbInfo
42161, 421613	`0x000000000000000000000000000000000000006D`	ArbAggregator
42161, 421613	`0x0000000000000000000000000000000000000068`	ArbFunctionTable
433114, 43113	`0x0200000000000000000000000000000000000000`	ContractDeployerAllowListAddress
433114, 43113	`0x0200000000000000000000000000000000000001`	ContractNativeMinterAddress
433114, 43113	`0x0200000000000000000000000000000000000002`	TxAllowListAddress
433114, 43113	`0x0200000000000000000000000000000000000003`	FeeConfigManagerAddress
ALL	`0x4e59b44847b379578588920cA78FbF26c0B4956C`	(Foundry) Create2Deployer
ALL	`0x7109709ECfa91a80626fF3989D68f67F5b1DD12D`	(Foundry) VM
ALL	`0x000000000000000000636F6e736F6c652e6c6f67`	(Foundry) Console

Reserved Ranges

Some chains also include reserved ranges for precompile contracts.

Chain ID	Start	Stop
ALL	`0x00`	`0xff`
433114, 43113	`0x0100000000000000000000000000000000000000`	`0x01000000000000000000000000000000000000ff`
433114, 43113	`0x0200000000000000000000000000000000000000`	`0x02000000000000000000000000000000000000ff`
433114, 43113	`0x0300000000000000000000000000000000000000`	`0x03000000000000000000000000000000000000ff`

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