Add test cleanup fixtures and remove global state

[bjarketol]

Summary

Closes #41

• Add pytest fixtures for automatic test cleanup
• Mark slow tests (wayve) with @pytest.mark.slow

Problem

Tests were leaving behind output directories (output_pywake_4wts/, output_test_foxes/, etc.) that accumulated over multiple runs.

Solution

Created tests/conftest.py with:

• Pre-cleanup fixture - Removes leftover output directories at session start
• output_dir fixture - Provides unique temp directory per test, cleans up on success, preserves on failure
• Failure tracking - Uses pytest hooks to detect failures and conditionally preserve output for debugging

Changes

File	Change
tests/conftest.py	New file with cleanup fixtures
tests/test_foxes.py	Use fixtures
tests/test_pywake.py	Use output_dir fixture
tests/test_cs.py	Use output_dir fixture
tests/test_wayve.py	Use output_dir fixture, add slow marker

Test plan

• Run uv run python -m pytest tests/ -m "not slow" - all 33 tests pass
• Verify no output_* directories remain after test run

[bjarketol]

@SchmJo can you review this? or what is the process?

[SchmJo]

I am not entirely sure why you are introducing conftest.py, which looks like a complication. Was the testing not running fine originally? Usually tests run as part of CI/CD , ie., github actions, and the leftover folders don't matter. That being said, I am of course happy with cleaning up after tests.

I also don't understand your special treatment of foxes engines, they should not matter for tests. My feeling is that I am missing something. Also, I do not feel comfortable reviewing the pywake part, I guess you need to catch Julian for this. The foxes part I can do, once I understand the main idea!

[bjarketol]

@SchmJo The main goals are:

• Avoid many folders on testing by letting tests perform a clean-up after tests pass
• Mark very slow tests, to optionally skip those for faster iteration cycles

I am happy to skip the foxes engine resetting, that was a minor thing.

[bjarketol]

@SchmJo I removed the foxes engine resetting and the engine argument to the tests.

Can you see if you are happy with the rest?

[bjarketol]

@kilojoules can you review the pywake part?

[SchmJo]

Thanks for your work on WIFA, I am still not sure why you are so interested in the tests - are they relevant for your own workflow?

[bjarketol]

@SchmJo @kilojoules can you take a look at this again?

If you prefer the old style of having explicit folders, let me know, then perhaps I can just add a cleaning step to each test instead?

[SchmJo]

The foxes part looks fine for me

[mathieu7an]

I am fine with the modifications. Should we merge this branch?

[kilojoules]

Looks good to me beyond the numpy 2 thing