Add Storage test

[ephess]

No description provided.

[BenSparksCode]

This looks solid! Nice use of Foundry's libs to find those storage slots.

The only thing I think we should add are checks of values set in the constructor - you have most of them, just missing INITIAL_CHAIN_ID and INITIAL_DOMAIN_SEPARATOR.

Because they're internal, you'll have to make a "dummy" contract at the bottom of the test file that inherits Storage, and then includes public functions you can call which return the values of those internal variables. You'll also need to implement _computeDomainSeparator() but maybe just make it return bytes32("SEPARATOR") and test that the var gets set correctly.

Here's an example of this inheritance thing to expose the internal functions of a contract for a test:
https://github.com/FastLane-Labs/atlas/blob/main/test/Permit69.t.sol#L260

[ephess]

Thanks Ben, I've implemented your suggestions. Appreciate the feedback.

Any thoughts on how to target the storage slots I haven't been able to test with the stdstore.target stuff? It's a bit confusing to me to try figure out how to chain these calls for more complex data structures. Perhaps it's more obvious to you.

I was planning on just leaving this as a TODO for a future punter.

[BenSparksCode]

Any thoughts on how to target the storage slots [...] for more complex data structures.

Yeah, it's very involved when you get into more complex data structures (combinations of mappings, structs, arrays).

I think we can leave that out for this PR and test file. The only reason I can think of to test around that sort of thing is to make sure that the caller and callee contracts in a delegatecall tx have the same storage layout so the correct data is targeted. But we'll do some tests that cover that in the parts of Atlas that delegatecall the lib contracts.
So I think this is great to merge as is. Good job!