Add unit and type tests

[MarcoArtiano]

Following #114, this PR adds unit and type stability tests.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.88%. Comparing base (9dd3b48) to head (aa421ab).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #117      +/-   ##
==========================================
+ Coverage   91.89%   96.88%   +4.98%     
==========================================
  Files          28       28              
  Lines        3073     3369     +296     
==========================================
+ Hits         2824     3264     +440     
+ Misses        249      105     -144     

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[ranocha]

Thanks! Could you please also add some type stability tests like in https://github.com/trixi-framework/Trixi.jl/blob/main/test/test_type.jl?

[ranocha]

Since it looks like this PR will become big: You don't have to add these tests for everything. It is also fine to add them for some equations and open an issue for the remaining ones.
(I should have written this earlier, sorry)

[MarcoArtiano]

Sorry, I didn't realize it became that big. I tried to cover as much as possible.

Some of the equations are still not fully tested (e.g. Moist and CovariantShallowWater), therefore I'll open an issue after this PR will be merged.

If you prefer I can divide this PR in a couple of PRs. Otherwise this is ready for a review.

[ranocha]

Thanks! You can already open the issue.

[ranocha]

Thanks!

[ranocha]

Thanks! It would be nice to get a review from one of the other developers as well, e.g., @amrueda, @benegee, or @tristanmontoya

[benegee]

Thanks a lot for putting so much effort into this! It is great to see such thorough unit tests and will be a perfect guideline for upcoming implementation. I will myself try to follow in #100.