feat: vm.assume support in invariant tests

[mds1]

Component

Forge

Describe the feature you would like

Invariant tests support this cheat, which I believe is because assume was added before invariant tests. There are two ways we should support:

• vm.assume directly in a function invariant_MyInvariantTest() method. Currently a failed assume here fails the test with [FAIL. Reason: Assertion failed.]. To be fair this usage is a bit limited since you can't make assumptions on fuzzed inputs, but still seems worthwhile to support
• vm.assume in a handler contract. This lets you reject e.g. owner addresses from a fuzzed owner input. I tried putting a quick test together and it seems these are just ignored since the cheat isn't being called in a test method

Additional context

No response

[PaulRBerg]

For historical context on this issue, see the discussion here:

foundry-rs/book#760 (comment)

[amarcu]

What are good ways to work around this issue for now? I'm considering using bound() to filter out addresses like address(0). Would love to be able to use vm.assume() in handler contracts. We're using the fail_on_revert = true flag for invariant tests and it would make everything a lot easier to manage.

[PaulRBerg]

The only workarounds for now are:

1. Use bound (as you suggested)
2. Good old if and return statements, e.g.

if (value == address(0) {
    return;
}