"InvariantTest" does not have a "vm"

[PaulRBerg]

No cheatcodes can currently be used in a test contract that inherits just from InvariantTest.

I don't know if this is intended - but if it is, we should definitely mention what's the recommend way of adding the vm (in foundry-rs/book#760), e.g. inherit from Test, or TestBase, define a vm yourself, etc.

[mds1]

You would inherit from both, e.g. MyInvariantTest is Test, InvariantTest. The latter just adds some invariant helper methods to your contract. Now that I think of it, I wonder if the content of InvariantTest should just be part of Test by default, wdyt? cc @gakonst @lucas-manuel for thoughts too

[lucas-manuel]

I think since invariants are a subset of overall testing it makes sense to do Test, InvariantTest. However if this is something that people will run into often I can see the argument for adding both the Test though.

Comes down to compilation time vs. ease of use I guess. What do you think is best here @mds1?

[PaulRBerg]

Now that I think of it, I wonder if the content of InvariantTest should just be part of Test by default, wdyt?

Works for me.

Comes down to compilation time vs. ease of use

Compilation times should not be a concern in this case - compiling a dozen or so functions should be a super quick task on modern computers.

[PaulRBerg]

Another benefit of merging InvariantTest with Test is that it would partially address this issue:

foundry-rs/foundry#4162

That is, invariant tests would no longer be considered something qualitatively different from fuzz tests - which makes sense, since inputs are fuzzed in invariants tests, too.

[gakonst]

Let's do contract Test is InvariantTest then?

[mds1]

I'm good with that. This would be a breaking change, so we'll release a v1.4.0 after?

[gakonst]

SGTM.

[Sabnock01]

Shouldn't the invariant testing utilities follow the same pattern as everything else?

i.e. have the file StdInvariant.sol inherited by Test.sol?

Very much in favor of keeping Test.sol as the superset as well.

[mds1]

i.e. have the file StdInvariant.sol inherited by Test.sol?

Yea this is what I was planning to do actually, will open a PR for it sometime this week

[mds1]

PR for this is ready here if anyone can give a quick review 🙂