fix: Resolve test collisions when capsys used

[davem-bis]

Description

Tests that use capsys can collide with each other as capsys is not threadsafe.

I have modified conftest.py to apply the isolated pytest marker (so they tests run sequentially) if capsys is passed to the test.

Test Plan

• make fast-test passes.

• PyTest correctly flags tests that use capsys as marked with isolated:

  

  Note that test_python_model_empty_df_raises does not have the isolated marker applied to it directly, it is dynamically added by the changes to conftest.

  

Checklist

• I have run make style and fixed any issues
• I have added tests for my changes (if applicable) (N/A)
• All existing tests pass (make fast-test)
• My commits are signed off (git commit -s) per the DCO

[cmgoffena13]

Appreciate you wanting to help stabilize the CI!

Something I noticed is we have capsys stuff in the slow tests as well. So to make sure we properly tag stuff you'd want to reorder the labeling in conftest.py like this:

for item in items:
    if "capsys" in item.fixturenames:
        item.add_marker("isolated")
    for marker in item.iter_markers():
        if marker.name in test_type_markers:
            break
    else:
        item.add_marker("fast")

And then we can modify the make commands to exclude isolated and just run them after:

fast-test:
	pytest -n auto -m "fast and not cicdonly and not isolated" --junitxml=test-results/junit-fast-test.xml && pytest -m "isolated and not slow" && pytest -m "registry_isolation" && pytest -m "dialect_isolated"

slow-test:
	pytest -n auto -m "(fast or slow) and not cicdonly and not isolated" && pytest -m "isolated" && pytest -m "registry_isolation" && pytest -m "dialect_isolated"

cicd-test:
	pytest -n auto -m "(fast or slow) and not pyspark and not isolated" --junitxml=test-results/junit-cicd.xml && pytest -m "pyspark" && pytest -m "isolated" && pytest -m "registry_isolation" && pytest -m "dialect_isolated"

That should address this issue regardless of fast, slow, or cicdonly!