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251 lines
8.3 KiB
Markdown
251 lines
8.3 KiB
Markdown
# Forge Standard Library • [](https://github.com/foundry-rs/forge-std/actions/workflows/ci.yml)
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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.
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**Learn how to use Forge-Std with the [📖 Foundry Book (Forge-Std Guide)](https://book.getfoundry.sh/forge/forge-std.html).**
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## Install
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```bash
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forge install foundry-rs/forge-std
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```
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## Contracts
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### stdError
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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 builtin errors.
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See the contract itself for all error codes.
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#### Example usage
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```solidity
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import "forge-std/Test.sol";
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contract TestContract is Test {
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ErrorsTest test;
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function setUp() public {
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test = new ErrorsTest();
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}
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function testExpectArithmetic() public {
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vm.expectRevert(stdError.arithmeticError);
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test.arithmeticError(10);
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}
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}
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contract ErrorsTest {
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function arithmeticError(uint256 a) public {
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uint256 a = a - 100;
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}
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}
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```
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### stdStorage
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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)`).
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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.
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I.e.:
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```solidity
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struct T {
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// depth 0
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uint256 a;
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// depth 1
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uint256 b;
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}
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```
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#### Example usage
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```solidity
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import "forge-std/Test.sol";
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contract TestContract is Test {
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using stdStorage for StdStorage;
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Storage test;
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function setUp() public {
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test = new Storage();
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}
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function testFindExists() public {
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// Lets say we want to find the slot for the public
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// variable `exists`. We just pass in the function selector
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// to the `find` command
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uint256 slot = stdstore.target(address(test)).sig("exists()").find();
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assertEq(slot, 0);
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}
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function testWriteExists() public {
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// Lets say we want to write to the slot for the public
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// variable `exists`. We just pass in the function selector
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// to the `checked_write` command
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stdstore.target(address(test)).sig("exists()").checked_write(100);
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assertEq(test.exists(), 100);
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}
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// It supports arbitrary storage layouts, like assembly based storage locations
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function testFindHidden() public {
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// `hidden` is a random hash of a bytes, iteration through slots would
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// not find it. Our mechanism does
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// Also, you can use the selector instead of a string
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uint256 slot = stdstore.target(address(test)).sig(test.hidden.selector).find();
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assertEq(slot, uint256(keccak256("my.random.var")));
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}
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// If targeting a mapping, you have to pass in the keys necessary to perform the find
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// i.e.:
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function testFindMapping() public {
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uint256 slot = stdstore
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.target(address(test))
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.sig(test.map_addr.selector)
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.with_key(address(this))
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.find();
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// in the `Storage` constructor, we wrote that this address' value was 1 in the map
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// so when we load the slot, we expect it to be 1
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assertEq(uint(vm.load(address(test), bytes32(slot))), 1);
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}
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// If the target is a struct, you can specify the field depth:
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function testFindStruct() public {
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// NOTE: see the depth parameter - 0 means 0th field, 1 means 1st field, etc.
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uint256 slot_for_a_field = stdstore
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.target(address(test))
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.sig(test.basicStruct.selector)
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.depth(0)
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.find();
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uint256 slot_for_b_field = stdstore
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.target(address(test))
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.sig(test.basicStruct.selector)
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.depth(1)
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.find();
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assertEq(uint(vm.load(address(test), bytes32(slot_for_a_field))), 1);
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assertEq(uint(vm.load(address(test), bytes32(slot_for_b_field))), 2);
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}
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}
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// A complex storage contract
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contract Storage {
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struct UnpackedStruct {
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uint256 a;
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uint256 b;
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}
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constructor() {
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map_addr[msg.sender] = 1;
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}
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uint256 public exists = 1;
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mapping(address => uint256) public map_addr;
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// mapping(address => Packed) public map_packed;
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mapping(address => UnpackedStruct) public map_struct;
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mapping(address => mapping(address => uint256)) public deep_map;
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mapping(address => mapping(address => UnpackedStruct)) public deep_map_struct;
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UnpackedStruct public basicStruct = UnpackedStruct({
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a: 1,
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b: 2
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});
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function hidden() public view returns (bytes32 t) {
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// an extremely hidden storage slot
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bytes32 slot = keccak256("my.random.var");
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assembly {
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t := sload(slot)
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}
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}
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}
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```
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### stdCheats
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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 address 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.
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#### Example usage:
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```solidity
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// SPDX-License-Identifier: MIT
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pragma solidity ^0.8.0;
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import "forge-std/Test.sol";
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// Inherit the stdCheats
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contract StdCheatsTest is Test {
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Bar test;
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function setUp() public {
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test = new Bar();
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}
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function testHoax() public {
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// we call `hoax`, which gives the target address
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// eth and then calls `prank`
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hoax(address(1337));
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test.bar{value: 100}(address(1337));
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// overloaded to allow you to specify how much eth to
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// initialize the address with
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hoax(address(1337), 1);
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test.bar{value: 1}(address(1337));
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}
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function testStartHoax() public {
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// we call `startHoax`, which gives the target address
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// eth and then calls `startPrank`
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//
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// it is also overloaded so that you can specify an eth amount
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startHoax(address(1337));
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test.bar{value: 100}(address(1337));
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test.bar{value: 100}(address(1337));
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vm.stopPrank();
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test.bar(address(this));
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}
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}
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contract Bar {
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function bar(address expectedSender) public payable {
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require(msg.sender == expectedSender, "!prank");
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}
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}
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```
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### Std Assertions
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Expand upon the assertion functions from the `DSTest` library.
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### `console.log`
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Usage follows the same format as [Hardhat](https://hardhat.org/hardhat-network/reference/#console-log).
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It's recommended to use `console2.sol` as shown below, as this will show the decoded logs in Forge traces.
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```solidity
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// import it indirectly via Test.sol
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import "forge-std/Test.sol";
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// or directly import it
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import "forge-std/console2.sol";
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...
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console2.log(someValue);
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```
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If you need compatibility with Hardhat, you must use the standard `console.sol` instead.
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Due to a bug in `console.sol`, logs that use `uint256` or `int256` types will not be properly decoded in Forge traces.
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```solidity
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// import it indirectly via Test.sol
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import "forge-std/Test.sol";
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// or directly import it
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import "forge-std/console.sol";
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...
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console.log(someValue);
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```
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## License
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Forge Standard Library is offered under either [MIT](LICENSE-MIT) or [Apache 2.0](LICENSE-APACHE) license.
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