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| # Forge Standard Library • [](https://github.com/foundry-rs/forge-std/actions/workflows/ci.yml) | |
| Forge Standard Library is a collection of helpful contracts and libraries for use with [Forge and Foundry](https://github.com/foundry-rs/foundry). It leverages Forge's cheatcodes to make writing tests easier and faster, while improving the UX of cheatcodes. | |
| **Learn how to use Forge-Std with the [📖 Foundry Book (Forge-Std Guide)](https://book.getfoundry.sh/forge/forge-std.html).** | |
| ## Install | |
| ```bash | |
| forge install foundry-rs/forge-std | |
| ``` | |
| ## Contracts | |
| ### stdError | |
| This is a helper contract for errors and reverts. In Forge, this contract is particularly helpful for the `expectRevert` cheatcode, as it provides all compiler built-in errors. | |
| See the contract itself for all error codes. | |
| #### Example usage | |
| ```solidity | |
| import "forge-std/Test.sol"; | |
| contract TestContract is Test { | |
| ErrorsTest test; | |
| function setUp() public { | |
| test = new ErrorsTest(); | |
| } | |
| function testExpectArithmetic() public { | |
| vm.expectRevert(stdError.arithmeticError); | |
| test.arithmeticError(10); | |
| } | |
| } | |
| contract ErrorsTest { | |
| function arithmeticError(uint256 a) public { | |
| a = a - 100; | |
| } | |
| } | |
| ``` | |
| ### stdStorage | |
| This is a rather large contract due to all of the overloading to make the UX decent. Primarily, it is a wrapper around the `record` and `accesses` cheatcodes. It can *always* find and write the storage slot(s) associated with a particular variable without knowing the storage layout. The one _major_ caveat to this is while a slot can be found for packed storage variables, we can't write to that variable safely. If a user tries to write to a packed slot, the execution throws an error, unless it is uninitialized (`bytes32(0)`). | |
| This works by recording all `SLOAD`s and `SSTORE`s during a function call. If there is a single slot read or written to, it immediately returns the slot. Otherwise, behind the scenes, we iterate through and check each one (assuming the user passed in a `depth` parameter). If the variable is a struct, you can pass in a `depth` parameter which is basically the field depth. | |
| I.e.: | |
| ```solidity | |
| struct T { | |
| // depth 0 | |
| uint256 a; | |
| // depth 1 | |
| uint256 b; | |
| } | |
| ``` | |
| #### Example usage | |
| ```solidity | |
| import "forge-std/Test.sol"; | |
| contract TestContract is Test { | |
| using stdStorage for StdStorage; | |
| Storage test; | |
| function setUp() public { | |
| test = new Storage(); | |
| } | |
| function testFindExists() public { | |
| // Lets say we want to find the slot for the public | |
| // variable `exists`. We just pass in the function selector | |
| // to the `find` command | |
| uint256 slot = stdstore.target(address(test)).sig("exists()").find(); | |
| assertEq(slot, 0); | |
| } | |
| function testWriteExists() public { | |
| // Lets say we want to write to the slot for the public | |
| // variable `exists`. We just pass in the function selector | |
| // to the `checked_write` command | |
| stdstore.target(address(test)).sig("exists()").checked_write(100); | |
| assertEq(test.exists(), 100); | |
| } | |
| // It supports arbitrary storage layouts, like assembly based storage locations | |
| function testFindHidden() public { | |
| // `hidden` is a random hash of a bytes, iteration through slots would | |
| // not find it. Our mechanism does | |
| // Also, you can use the selector instead of a string | |
| uint256 slot = stdstore.target(address(test)).sig(test.hidden.selector).find(); | |
| assertEq(slot, uint256(keccak256("my.random.var"))); | |
| } | |
| // If targeting a mapping, you have to pass in the keys necessary to perform the find | |
| // i.e.: | |
| function testFindMapping() public { | |
| uint256 slot = stdstore | |
| .target(address(test)) | |
| .sig(test.map_addr.selector) | |
| .with_key(address(this)) | |
| .find(); | |
| // in the `Storage` constructor, we wrote that this address' value was 1 in the map | |
| // so when we load the slot, we expect it to be 1 | |
| assertEq(uint(vm.load(address(test), bytes32(slot))), 1); | |
| } | |
| // If the target is a struct, you can specify the field depth: | |
| function testFindStruct() public { | |
| // NOTE: see the depth parameter - 0 means 0th field, 1 means 1st field, etc. | |
| uint256 slot_for_a_field = stdstore | |
| .target(address(test)) | |
| .sig(test.basicStruct.selector) | |
| .depth(0) | |
| .find(); | |
| uint256 slot_for_b_field = stdstore | |
| .target(address(test)) | |
| .sig(test.basicStruct.selector) | |
| .depth(1) | |
| .find(); | |
| assertEq(uint(vm.load(address(test), bytes32(slot_for_a_field))), 1); | |
| assertEq(uint(vm.load(address(test), bytes32(slot_for_b_field))), 2); | |
| } | |
| } | |
| // A complex storage contract | |
| contract Storage { | |
| struct UnpackedStruct { | |
| uint256 a; | |
| uint256 b; | |
| } | |
| constructor() { | |
| map_addr[msg.sender] = 1; | |
| } | |
| uint256 public exists = 1; | |
| mapping(address => uint256) public map_addr; | |
| // mapping(address => Packed) public map_packed; | |
| mapping(address => UnpackedStruct) public map_struct; | |
| mapping(address => mapping(address => uint256)) public deep_map; | |
| mapping(address => mapping(address => UnpackedStruct)) public deep_map_struct; | |
| UnpackedStruct public basicStruct = UnpackedStruct({ | |
| a: 1, | |
| b: 2 | |
| }); | |
| function hidden() public view returns (bytes32 t) { | |
| // an extremely hidden storage slot | |
| bytes32 slot = keccak256("my.random.var"); | |
| assembly { | |
| t := sload(slot) | |
| } | |
| } | |
| } | |
| ``` | |
| ### stdCheats | |
| This is a wrapper over miscellaneous cheatcodes that need wrappers to be more dev friendly. Currently there are only functions related to `prank`. In general, users may expect ETH to be put into an address on `prank`, but this is not the case for safety reasons. Explicitly this `hoax` function should only be used for addresses that have expected balances as it will get overwritten. If an address already has ETH, you should just use `prank`. If you want to change that balance explicitly, just use `deal`. If you want to do both, `hoax` is also right for you. | |
| #### Example usage: | |
| ```solidity | |
| // SPDX-License-Identifier: MIT | |
| pragma solidity ^0.8.0; | |
| import "forge-std/Test.sol"; | |
| // Inherit the stdCheats | |
| contract StdCheatsTest is Test { | |
| Bar test; | |
| function setUp() public { | |
| test = new Bar(); | |
| } | |
| function testHoax() public { | |
| // we call `hoax`, which gives the target address | |
| // eth and then calls `prank` | |
| hoax(address(1337)); | |
| test.bar{value: 100}(address(1337)); | |
| // overloaded to allow you to specify how much eth to | |
| // initialize the address with | |
| hoax(address(1337), 1); | |
| test.bar{value: 1}(address(1337)); | |
| } | |
| function testStartHoax() public { | |
| // we call `startHoax`, which gives the target address | |
| // eth and then calls `startPrank` | |
| // | |
| // it is also overloaded so that you can specify an eth amount | |
| startHoax(address(1337)); | |
| test.bar{value: 100}(address(1337)); | |
| test.bar{value: 100}(address(1337)); | |
| vm.stopPrank(); | |
| test.bar(address(this)); | |
| } | |
| } | |
| contract Bar { | |
| function bar(address expectedSender) public payable { | |
| require(msg.sender == expectedSender, "!prank"); | |
| } | |
| } | |
| ``` | |
| ### Std Assertions | |
| Contains various assertions. | |
| ### `console.log` | |
| Usage follows the same format as [Hardhat](https://hardhat.org/hardhat-network/reference/#console-log). | |
| It's recommended to use `console2.sol` as shown below, as this will show the decoded logs in Forge traces. | |
| ```solidity | |
| // import it indirectly via Test.sol | |
| import "forge-std/Test.sol"; | |
| // or directly import it | |
| import "forge-std/console2.sol"; | |
| ... | |
| console2.log(someValue); | |
| ``` | |
| If you need compatibility with Hardhat, you must use the standard `console.sol` instead. | |
| Due to a bug in `console.sol`, logs that use `uint256` or `int256` types will not be properly decoded in Forge traces. | |
| ```solidity | |
| // import it indirectly via Test.sol | |
| import "forge-std/Test.sol"; | |
| // or directly import it | |
| import "forge-std/console.sol"; | |
| ... | |
| console.log(someValue); | |
| ``` | |
| ## Contributing | |
| See our [contributing guidelines](./CONTRIBUTING.md). | |
| ## Getting Help | |
| First, see if the answer to your question can be found in [book](https://book.getfoundry.sh). | |
| If the answer is not there: | |
| - Join the [support Telegram](https://t.me/foundry_support) to get help, or | |
| - Open a [discussion](https://github.com/foundry-rs/foundry/discussions/new/choose) with your question, or | |
| - Open an issue with [the bug](https://github.com/foundry-rs/foundry/issues/new/choose) | |
| If you want to contribute, or follow along with contributor discussion, you can use our [main telegram](https://t.me/foundry_rs) to chat with us about the development of Foundry! | |
| ## License | |
| Forge Standard Library is offered under either [MIT](LICENSE-MIT) or [Apache 2.0](LICENSE-APACHE) license. | |