misleading error message on failed expectEmit cheat code

[devtooligan]

Component

Forge

Have you ensured that all of these are up to date?

• Foundry
• Foundryup

What version of Foundry are you on?

forge 0.1.0 (05eb664 2022-03-07T00:08:24.917561+00:00)

What command(s) is the bug in?

forge test

Operating System

macOS (M1)

Describe the bug

After invoking the expectEmit cheatcode, if any of the topics or data in the log does not match what was expected, it gives a misleading fail message, FAIL. Reason: Expected an emit, but no logs were emitted afterward

In my example, I had coded:

        vm.expectEmit(true, true, true, true);
        emit Liquidity(maturity, user2, user1, address(0), -INITIAL_BASE, 0, INITIAL_BASE);

but I made a mistake, the 3rd parameter shouldve been user2.

I got this:

It would be nice to have a better message - at least something like "topics or data did not match what was expected" or even better if we could show exactly what was wrong, e.g. "Expected 0xabcbcbcbcb for topic2 but got 0x010191911991"

[mds1]

Seems there may have been an expectEmit regression at some point? In #592 the failure message was Reason: Log != expected log, but I've just confirmed on forge 0.1.0 (f01d2f7 2022-03-11T00:04:44.960707+00:00) that when topics don't match I get the same no logs were emitted error

[onbjerg]

Damn the expectEmit issues are stacking up. I would love a tracking issue of some sort so I can fix them during/after the REVM port.

FWIW this is probably a regression as @mds1 pointed out. The error message is for when you call expectEmit but do not emit a log afterwards, which you seem to be doing.

[onbjerg]

I can't reproduce this anymore:

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.13;

import "forge-std/Test.sol";

contract A {
    event Test(uint256 a);

    function b() external {
        emit Test(1);
    }
}

contract ContractTest is Test {
    event Test(uint256 a);

    function testExample() public {
        A a = new A();

        vm.expectEmit(false, true, false, true);
        emit Test(2);
        a.b();
    }
}

$ forge test
[⠢] Compiling...
No files changed, compilation skipped

Running 1 test for test/Contract.t.sol:ContractTest
[FAIL. Reason: Log != expected log] testExample() (gas: 70178)
Test result: FAILED. 0 passed; 1 failed; finished in 366.41µs

Failed tests:
[FAIL. Reason: Log != expected log] testExample() (gas: 70178)

Encountered a total of 1 failing tests, 0 tests succeeded

Because of this I am going to close this issue: improved error messages for expectEmit is tracked in #592. Let me know if this is still an issue for you 😄

[kwamentw]

hi @onbjerg,
I am getting this same issue after evoking my vm.expectEmit() in my test script, When running the test you can see the values emit, but the error tells you it expected an Emit whilst there was an emit, So i do not know whether foundry can detect the emit or I am just doing something wrong. My test script and error is below ;

error:

$ forge test --mt testEmitEventTrycatch -vvvvvvv
[⠰] Compiling...
[⠃] Compiling 2 files with 0.8.20
[⠒] Solc 0.8.20 finished in 1.48s
Compiler run successful!

Running 1 test for test/TestTryCatch.t.sol:TryCatchTest
[FAIL. Reason: Expected an emit, but the call reverted instead. Ensure you're testing the happy path when using the `expectEmit` cheatcode.] testEmitEventTrycatch() (gas: 11742)
Traces:
  [273525] TryCatchTest::setUp() 
    ├─ [218863] → new TryCatchEg@0x5615dEB798BB3E4dFa0139dFa1b3D433Cc23b72f
    │   └─ ← 1093 bytes of code
    └─ ← ()

  [11742] TryCatchTest::testEmitEventTrycatch() 
    ├─ [0] VM::expectEmit() 
    │   └─ ← ()
    ├─ [3701] TryCatchEg::LetsTryCatch(21, 4234) 
    │   ├─ [411] TryCatchEg::Add(21, 4234) [staticcall]
    │   │   └─ ← 4255
    │   ├─ emit ShowResult(result: 4255)
    │   ├─ emit Log(message: Add successful)
    │   └─ ← ()
    └─ ← "Log != expected log"

Test result: FAILED. 0 passed; 1 failed; 0 skipped; finished in 610.74µs
 
Ran 1 test suites: 0 tests passed, 1 failed, 0 skipped (1 total tests)

Failing tests:
Encountered 1 failing test in test/TestTryCatch.t.sol:TryCatchTest
[FAIL. Reason: Expected an emit, but the call reverted instead. Ensure you're testing the happy path when using the `expectEmit` cheatcode.] testEmitEventTrycatch() (gas: 11742)

Encountered a total of 1 failing tests, 0 tests succeeded

my test script:

    function testEmitEventTrycatch() public {
        vm.expectEmit();
        egoftrycatch.LetsTryCatch(21, 4234);
    }

The function I am testing:

function LetsTryCatch(uint256 firstDigit, uint256 secondDigit) external {
        try this.Add(firstDigit, secondDigit) returns (uint256 result) {
            emit ShowResult(result);
            emit Log("Add successful");
        } catch Error(string memory errorMessage) {
            emit Log(errorMessage);
            // revert(errorMessage);
        } catch (bytes memory errorData) {
            emit Log(string(errorData));
            // revert(string(errorData));
        }
    }

Thanks in advance