Improve test isolation and pytest integration

[elronbandel]

Previously, pytest would instantiate all test classes during discovery, which caused every backend to be loaded including heavy ones like the huggingface backend loading 8B model.

Now, tests can be scanned without eagerly realizing all backend. This means that missing dependencies or a faulty backend no longer block discovery: the remaining tests are still visible and runnable.

As a result, you can run and debug tests with VSCode tests extension (or other pytest integrations) without crashes or unnecessary loading of large models on every code change.

[avinash2692]

Hi @elronbandel:

• The API for validate might have changed since you last pushed. I think merging with main will solve this.
• I also got these errors when I ran the tests:

====================================================================== short test summary info ======================================================================
FAILED test/backends/test_huggingface.py::test_constraint_lora_with_requirement - TypeError: MelleaSession.validate() got an unexpected keyword argument 'return_full_validation_results'
FAILED test/backends/test_huggingface.py::test_constraint_lora_override - TypeError: MelleaSession.validate() got an unexpected keyword argument 'return_full_validation_results'
FAILED test/backends/test_huggingface.py::test_constraint_lora_override_does_not_override_alora - TypeError: MelleaSession.validate() got an unexpected keyword argument 'return_full_validation_results'
FAILED test/backends/test_huggingface.py::test_llmaj_req_does_not_use_alora - TypeError: MelleaSession.validate() got an unexpected keyword argument 'return_full_validation_results'
FAILED test/stdlib_basics/test_genslot.py::test_func - NameError: name 'i' is not defined
ERROR test/stdlib_basics/test_genslot.py::test_gen_slot_output - NameError: name 'i' is not defined
ERROR test/stdlib_basics/test_genslot.py::test_sentiment_output - NameError: name 'i' is not defined

The first half is cause of validate but can't seem to figure out where the second half is coming from.

[avinash2692]

return_full_validation_results might be invalid because of #54. Can you remove this in all the tests?

[jakelorocco]

@elronbandel, not sure if this makes things easier / makes sense, but most of the backend tests are very similar. It might make sense to move all of the common tests to one file and just parameterize the session / backend. I took a shot at it in the old repo, but kept getting sidetracked by other high priority work. No need to incorporate any of it or this suggestion.