Add unit-tests to resolve

[Weibye]

Objective

A tiny step towards #92, but mostly I need to see where things are breaking when working on #160 and building unit-test helps.

Feedback wanted

Not quite sure if these are considered good tests as they feel a tiny bit arbitrary in terms of which magical numbers to test for, so any feedback is welcome :)

[TimJentzsch]

The cases are not that fun to review because the lines are so long that they wrap and GitHub and they don't have syntax highlighting, but we probably can't fix that.

Anyway, seems solid for me. The resolve_size one has a lot of cases, I wonder if the property based testing frameworks that @alice-i-cecile recommended would help with that? I haven't looked into them yet.

In any case, it's good to see more unit tests, that will definitely help with refactoring and optimizations!

[alice-i-cecile]

Not the prettiest, but I think this is good for now.

Merging to make refactors easier.

[mcrvaz]

I was thinking of doing some tests just like this ones for the remaining public functions in this file.
Is this the expected test format?
Should we keep tests in the same file as the feature or separate them?

[alice-i-cecile]

I was thinking of doing some tests just like this ones for the remaining public functions in this file.

Yes please!

Is this the expected test format?

This seems like a nice format; we can use it for consistency but feel free to raise concerns that you have.

Should we keep tests in the same file as the feature or separate them?

For unit tests of internal functionality like this, keep them in the same file as they're defined. Integration tests belong in the root level test folder.