I'd actually call the real procedure, not a copy of it. I think the asset conversion tests are a good example which show how to do this so that you don't have to run a full transaction.

I think it would be cleaner if we had the assert_eq! in Rust as opposed to running the test logic in masm. I think it reads easier if you call the masm procedure, get the returned values off the stack in Rust, then check the two Rust variable values are equal. As noted above, we have this testing functions available in the agglayer crate, check out the asset_conversion.rs file to see how they are used

I recall that we had a discussion about whether we should use asserts in the Rust code vs MASM code, but IIRC we agreed to follow @PhilippGackstatter 's proposal to use asserts in the MASM code, but honestly I don't remember why. Probably to make the code self-contained and, which is more important, to check the error messages correctness in case the testing code uses some of the internal kernel/protocol procedures.

I think we discussed it at some point, but don't recall the outcome. I think there are pros and cons. Multiple asserts in MASM read relatively nicely and can be done sequentially, as done in this test.

On the other hand, asserts in Rust generally result in a better error when they fail. The downside is if you need to assert the correctness of multiple values, you sometimes need to write extra MASM to arrange the output stack appropriately and then also extract multiple stack values in the right order from the ExecutionOutput, which is messy and incurs unnecessary mental load to review its correctness.

So, I'd use whichever approach results in a more readable and easily maintainble test and one that provides good errors when it fails.