Please provide a small solidity code that shows an assertion failure that needs this new feature. We will show you how to add a test

Please provide a small solidity code that shows an assertion failure that needs this new feature. We will show you how to add a test

Something like this?

contract EventAssert {
    event ValueSet(uint256 indexed value);

    function setValue(uint256 value) public {
        emit ValueSet(value);
        assert(value != 1295);
    }
}

Your example needs to have an event emmited with a value that can be used to trigger the assertion, but it needs to be essential for that. Usually you need to do some computation and emit some value from it, that is normally hidden from the fuzzer.

How about this @gustavo-grieco?

contract EventAssert {
    uint private secret = 123;
    event Output(uint result);

    function check(uint x) public {
        uint result = x % 200;
        emit Output(result);
        if (result == secret) {
            assert(false);
        }
    }
}

Uhm it looks bette but I'm not sure the value from the event is useful to break the assertion. Try using a hashed value instead 🤔

So, something like this:

contract EventAssert {
    uint private secret;

    event Computed(uint result);

    constructor() {
        secret = uint(keccak256(abi.encodePacked(block.timestamp))) % 1000;
    }

    function check(uint x) public {
        uint result = (x * 3 + 7) % 1000;
        emit Computed(result);
        if (result == secret) {
            assert(false);
        }
    }
}

So if you remove emit Computed(result), echidna will not able to find the value to break it, right? (I haven't tested it)

So if you remove emit Computed(result), echidna will not able to find the value to break it, right? (I haven't tested it)

I think so, because if we don't emit, Echidna has no way of knowing about it.

Let me know how to go further with the testing.

Changed the contract following @elopez's suggestion:

contract EventAssert {
    uint private secret;
    event Secret(uint result);
    function reset() public {
        secret = uint(keccak256(abi.encodePacked(block.timestamp)));
        emit Secret(secret);
    }
    function check(uint x) public {
        if (x == secret) {
            assert(false);
        }
    }
}

This is the result:

On the left is upstream Echidna without the changes, and on the right is my fork:

This looks good, let's add it as a test in the "value" section

The fork doesn't reproduce the revert deterministically though, but I guess that's expected because of the hash being quite a huge one.

You mean that this test is not reliable ?

You mean that this test is not reliable ?

I wasn't sure if that's expected ir not. It only gives the output I sent a few times and at other times it doesn't revert and says everything passes.