fix(forge): replay fuzz failure only if same test selector (#11947)

Author: grandizzy

crates/evm/evm/src/executors/fuzz/mod.rs

@@ -141,8 +141,10 @@ impl FuzzedExecutor {
 
         'stop: while continue_campaign(test_data.runs) {
             // If counterexample recorded, replay it first, without incrementing runs.
-            let input = if let Some(failure) = self.persisted_failure.take() {
-                failure.calldata
+            let input = if let Some(failure) = self.persisted_failure.take()
+                && func.selector() == failure.calldata[..4]
+            {
+                failure.calldata.clone()
             } else {
                 // If running with progress, then increment current run.
                 if let Some(progress) = progress {
@@ -222,8 +224,9 @@ impl FuzzedExecutor {
                             break 'stop;
                         }
                         TestCaseError::Reject(_) => {
-                            // Discard run and apply max rejects if configured.
-                            test_data.runs -= 1;
+                            // Discard run and apply max rejects if configured. Saturate to handle
+                            // the case of replayed failure, which doesn't count as a run.
+                            test_data.runs = test_data.runs.saturating_sub(1);
                             if self.config.max_test_rejects > 0 {
                                 test_data.rejects += 1;
                                 if test_data.rejects >= self.config.max_test_rejects {

crates/forge/tests/it/fuzz.rs

@@ -391,3 +391,106 @@ Ran 1 test suite [ELAPSED]: 1 tests passed, 0 failed, 0 skipped (1 total tests)
 
 "#]]);
 });
+
+// Test that counterexample is not replayed if test changes.
+// <https://github.com/foundry-rs/foundry/issues/11927>
+forgetest_init!(test_fuzz_replay_with_changed_test, |prj, cmd| {
+    prj.update_config(|config| config.fuzz.seed = Some(U256::from(100u32)));
+    prj.add_test(
+        "Counter.t.sol",
+        r#"
+import {Test} from "forge-std/Test.sol";
+
+contract CounterTest is Test {
+    function testFuzz_SetNumber(uint256 x) public pure {
+        require(x > 200);
+    }
+}
+   "#,
+    );
+    // Tests should fail and record counterexample with value 2.
+    cmd.args(["test"]).assert_failure().stdout_eq(str![[r#"
+...
+Failing tests:
+Encountered 1 failing test in test/Counter.t.sol:CounterTest
+[FAIL: EvmError: Revert; counterexample: calldata=0x5c7f60d70000000000000000000000000000000000000000000000000000000000000002 args=[2]] testFuzz_SetNumber(uint256) (runs: 19, [AVG_GAS])
+...
+
+"#]]);
+
+    // Change test to assume counterexample 2 is discarded.
+    prj.add_test(
+        "Counter.t.sol",
+        r#"
+import {Test} from "forge-std/Test.sol";
+
+contract CounterTest is Test {
+    function testFuzz_SetNumber(uint256 x) public pure {
+        vm.assume(x != 2);
+    }
+}
+   "#,
+    );
+    // Test should pass when replay failure with changed assume logic.
+    cmd.forge_fuse().args(["test"]).assert_success().stdout_eq(str![[r#"
+[COMPILING_FILES] with [SOLC_VERSION]
+[SOLC_VERSION] [ELAPSED]
+Compiler run successful!
+
+Ran 1 test for test/Counter.t.sol:CounterTest
+[PASS] testFuzz_SetNumber(uint256) (runs: 256, [AVG_GAS])
+Suite result: ok. 1 passed; 0 failed; 0 skipped; [ELAPSED]
+
+Ran 1 test suite [ELAPSED]: 1 tests passed, 0 failed, 0 skipped (1 total tests)
+
+"#]]);
+
+    // Change test signature.
+    prj.add_test(
+        "Counter.t.sol",
+        r#"
+import {Test} from "forge-std/Test.sol";
+
+contract CounterTest is Test {
+    function testFuzz_SetNumber(uint8 x) public pure {
+    }
+}
+   "#,
+    );
+    // Test should pass when replay failure with changed function signature.
+    cmd.forge_fuse().args(["test"]).assert_success().stdout_eq(str![[r#"
+[COMPILING_FILES] with [SOLC_VERSION]
+[SOLC_VERSION] [ELAPSED]
+Compiler run successful!
+
+Ran 1 test for test/Counter.t.sol:CounterTest
+[PASS] testFuzz_SetNumber(uint8) (runs: 256, [AVG_GAS])
+Suite result: ok. 1 passed; 0 failed; 0 skipped; [ELAPSED]
+
+Ran 1 test suite [ELAPSED]: 1 tests passed, 0 failed, 0 skipped (1 total tests)
+
+"#]]);
+
+    // Change test back to the original one that produced the counterexample.
+    prj.add_test(
+        "Counter.t.sol",
+        r#"
+import {Test} from "forge-std/Test.sol";
+
+contract CounterTest is Test {
+    function testFuzz_SetNumber(uint256 x) public pure {
+        require(x > 200);
+    }
+}
+   "#,
+    );
+    // Test should fail with replayed counterexample 2 (0 runs).
+    cmd.forge_fuse().args(["test"]).assert_failure().stdout_eq(str![[r#"
+...
+Failing tests:
+Encountered 1 failing test in test/Counter.t.sol:CounterTest
+[FAIL: EvmError: Revert; counterexample: calldata=0x5c7f60d70000000000000000000000000000000000000000000000000000000000000002 args=[2]] testFuzz_SetNumber(uint256) (runs: 0, [AVG_GAS])
+...
+
+"#]]);
+});