feat(cheatcodes): add vm.expectMockCall to enforce that a mocked function is called with certain arguments

[JasoonS]

Component

Forge

Describe the feature you would like

Currently tests don't break if a mocked function is called with different arguments to what was expected.

Currently for example:

    cheats.mockCall(
      address(mocker),
      abi.encodeWithSelector(
        SomeContract.someFunction.selector,
        5
      ),
      abi.encode(6)
    );

With the above code it will return 6 if the function is called with an argument of 5 or anything else, additionally it won't fail if it isn't called with 5 (which is something you sometimes want to check.

I propose adding a function called something like mockCallStrict to the cheats so that tests can be more strict about this.

Additional context

This is a feature of Smock: https://smock.readthedocs.io/en/latest/fakes.html#asserting-call-arguments

[onbjerg]

You might be interested in expectCall instead. I don't think mockCall should be a superset of expectCall. Sometimes you definitely do want to only mock for a certain parameter, but still retain the ability to get real data for all other cases. If you want a stricter version perhaps this is a good addition to Forge Std instead as a wrapper around expectCall + mockCall

[gakonst]

adding a mock+expect combination in forge-std makes sense to me

[JasoonS]

Thanks, that makes sense to me too.

I won't make any changes to the std lib right now, but I'm working on some code-gen stuff that might be useful for others once it is done to assist with mocking.
Maybe that can be upstreamed at some point if it is useful.

[JasoonS]

Also FYI - my codegen work will allow mocking of internal functions without needing to move the the REVM as mentioned in this PR - #432 .

Like I say, I'll definitely share my work on that in the coming weeks/months 👍

[onbjerg]

@brockelmore Perhaps we should transfer this to Forge Std as well? Or maybe just close it and open up a new issue? Wdyt?

[mds1]

Per #3782, I'm going to move this back to the foundry repo

I'm also not too clear on the exact proposal here, I'd be curious to see sample code of that the cheat/UX would look like

[grandizzy]

@JasoonS please reopen this if still needed and provide a sample code of that the cheat/UX would look like as mentioned in above comment. thank you!

[deluca-mike]

@grandizzy

It would be nice to have this:

vm.expectAndMockCall(
    inboxes_[0],
    abi.encodeWithSelector(
        MockERC20Inbox.sendContractTransaction.selector,
        100_001,
        1_000_000,
        _appChainGateway,
        0,
        abi.encodeCall(IAppChainGatewayLike.receiveParameters, (0, keyChains_, values_))
    ),
    abi.encode(uint256(11))
);

instead of this:

vm.expectCall(
    inboxes_[0],
    abi.encodeWithSelector(
        MockERC20Inbox.sendContractTransaction.selector,
        100_000,
        1_000_000,
        _appChainGateway,
        0,
        abi.encodeCall(IAppChainGatewayLike.receiveParameters, (0, keyChains_, values_))
    )
);

vm.mockCall(
    inboxes_[0],
    abi.encodeWithSelector(
        MockERC20Inbox.sendContractTransaction.selector,
        100_001,
        1_000_000,
        _appChainGateway,
        0,
        abi.encodeCall(IAppChainGatewayLike.receiveParameters, (0, keyChains_, values_))
    ),
    abi.encode(uint256(11))
);

Sure, we could make a helper function:

function _expectAndMockCall(address callee, bytes memory data, bytes memory returnData) internal {
    vm.expectCall(callee, data);
    vm.mockCall(callee, data, returnData);
}

but foundry and forge-std is that helper tooling, so it probably makes sense that it lives there.