Foundry 中文

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 1 will delete snapshots with ids 2, 3, etc.)

Examples

struct Storage {
    uint slot0;
    uint slot1;
}

contract SnapshotTest is Test {
    Cheats constant cheats = Cheats(HEVM_ADDRESS);

    Storage store;

    function setUp() public {
        store.slot0 = 10;
        store.slot1 = 20;
    }

    function testSnapshot() public {
        uint256 snapshot = cheats.snapshot();
        store.slot0 = 300;
        store.slot1 = 400;

        assertEq(store.slot0, 300);
        assertEq(store.slot1, 400);

        // after resetting to a snapshot all changes are discarded
        cheats.revertTo(snapshot);
        assertEq(store.slot0, 10, "snapshot revert for slot 0 unsuccessful");
        assertEq(store.slot1, 20, "snapshot revert for slot 1 unsuccessful");
    }

}