Feat: snapshot and revertTo cheatcodes (#276)

chain/standard_cheat_code_contract.go

@@ -283,6 +283,27 @@ func getStandardCheatCodeContract(tracer *cheatCodeTracer) (*CheatCodeContract,
 		},
 	)
 
+	// snapshot: Takes a snapshot of the current state of the evm and returns the id associated with the snapshot
+	contract.addMethod(
+		"snapshot", abi.Arguments{}, abi.Arguments{{Type: typeUint256}},
+		func(tracer *cheatCodeTracer, inputs []any) ([]any, *cheatCodeRawReturnData) {
+			snapshotID := tracer.evm.StateDB.Snapshot()
+
+			return []any{snapshotID}, nil
+		},
+	)
+
+	// revertTo(uint256): Revert the state of the evm to a previous snapshot. Takes the snapshot id to revert to.
+	contract.addMethod(
+		"revertTo", abi.Arguments{{Type: typeUint256}}, abi.Arguments{{Type: typeBool}},
+		func(tracer *cheatCodeTracer, inputs []any) ([]any, *cheatCodeRawReturnData) {
+			snapshotID := inputs[0].(*big.Int)
+			tracer.evm.StateDB.RevertToSnapshot(int(snapshotID.Int64()))
+
+			return []any{true}, nil
+		},
+	)
+
 	// FFI: Run arbitrary command on base OS
 	contract.addMethod(
 		"ffi", abi.Arguments{{Type: typeStringSlice}}, abi.Arguments{{Type: typeBytes}},

fuzzing/fuzzer_test.go

@@ -208,6 +208,7 @@ func TestCheatCodes(t *testing.T) {
 		"testdata/contracts/cheat_codes/utils/to_string.sol",
 		"testdata/contracts/cheat_codes/utils/sign.sol",
 		"testdata/contracts/cheat_codes/utils/parse.sol",
+		"testdata/contracts/cheat_codes/vm/snapshot_and_revert_to.sol",
 		"testdata/contracts/cheat_codes/vm/coinbase.sol",
 		"testdata/contracts/cheat_codes/vm/chain_id.sol",
 		"testdata/contracts/cheat_codes/vm/deal.sol",

fuzzing/testdata/contracts/cheat_codes/vm/snapshot_and_revert_to.sol

@@ -0,0 +1,58 @@
+// This test ensures that we can take a snapshot of the current state of the testchain and revert to the state at that snapshot using the snapshot and revertTo cheatcodes
+pragma solidity ^0.8.0;
+
+interface CheatCodes {
+    function warp(uint256) external;
+
+    function deal(address, uint256) external;
+
+    function snapshot() external returns (uint256);
+
+    function revertTo(uint256) external returns (bool);
+}
+
+struct Storage {
+    uint slot0;
+    uint slot1;
+}
+
+contract TestContract {
+    Storage store;
+    uint256 timestamp;
+
+    function test() public {
+        // Obtain our cheat code contract reference.
+        CheatCodes cheats = CheatCodes(
+            0x7109709ECfa91a80626fF3989D68f67F5b1DD12D
+        );
+
+        store.slot0 = 10;
+        store.slot1 = 20;
+        timestamp = block.timestamp;
+        cheats.deal(address(this), 5 ether);
+
+        // Save state
+        uint256 snapshot = cheats.snapshot();
+
+        // Change state
+        store.slot0 = 300;
+        store.slot1 = 400;
+        cheats.deal(address(this), 500 ether);
+        cheats.warp(12345);
+
+        // Assert that state has been changed
+        assert(store.slot0 == 300);
+        assert(store.slot1 == 400);
+        assert(address(this).balance == 500 ether);
+        assert(block.timestamp == 12345);
+
+        // Revert to snapshot
+        cheats.revertTo(snapshot);
+
+        // Ensure state has been reset
+        assert(store.slot0 == 10);
+        assert(store.slot1 == 20);
+        assert(address(this).balance == 5 ether);
+        assert(block.timestamp == timestamp);
+    }
+}