Stateful testing: Compare SystemUnderTest to State?

[andrewjstone]

Hi,

I really like gopter so far. Thanks for providing such a useful library. I've just run into something unexpected with stateful testing though.

What I want is after each operation to not only compare the Result of the SystemUnderTest command with the model state (State) as in Postcondition, but also to ensure that the internal state of the SystemUnderTest is logically equivalent to the model state. I tried including a pointer to the SystemUnderTest in State so I could just perform this check in Postcondition, but it appears that by the time Postcondition runs, the pointer is pointing to a different value than what was initialized and returned from NewSystemUnderTest.

The rationale for this feature is to be able to test mutable methods on types that don't return values. So far I think the only workaround is to provide some introspection methods that we add as commands so we can then run and compare the output to the model state.

I was wondering if you could provide this capability, via another callback like invariant/1 in eqc_statem, or if there is a specific reason you think it should not be included. And yes, effort is a fine justification :) Thanks!

[andrewjstone]

It looks like I can just return the SystemUnderTest as part of Result when Run is called. That actually makes more sense than what I was originally trying to do. Sorry for the bother.