[FEATURE] [JOSS] Consider using pytest groups

[HaoZeke]

Problem you'd like to address and suggestion
Related to the discussion in #100, perhaps the design would benefit from separating the tests into classes which require specific devices or not.

Additional context
Another "not necessarily actionable" point for JOSS, just one to keep in mind.

[mdmeeker]

I'm leaning towards leaving the test suite as is since there are very few tests which require an available CUDA device. These are currently marked with skipif's which are conditional on the availability of a CUDA device via PyTorch and set to name the absence of a usable CUDA device as the reason for these being skipped in the pytest output.

I think this approach is more convenient overall for now, but I do agree that it will probably make more sense to introduce separate classes whenever the test suite is expanded.