Clean up legacy test scaffolding in cudf-polars

[madsbk]

Description

Removes assert_collect_raises, its callers, and the leftover executor=-era keyword plumbing that is no longer used anywhere else.

[madsbk]

never used

[madsbk]

Inlining, the function is only called once now.

[madsbk]

Inlining the function is simpler to understand IMO. We now just do:

-        assert_collect_raises(
-            q,
-            cudf_except=pl.exceptions.ComputeError,
-            polars_except=pl.exceptions.InvalidOperationError,
-        )
+        with pytest.raises(pl.exceptions.InvalidOperationError):
+            q.collect()
+        with pytest.raises(pl.exceptions.ComputeError):
+            q.collect(engine=pl.GPUEngine(executor="in-memory", raise_on_fail=True))

[coderabbitai]

📝 Walkthrough

Summary by CodeRabbit

• Refactor
  • Simplified internal testing infrastructure and assertion utilities for improved code maintainability.

Walkthrough

This PR simplifies the cuDF Polars test assertion API by removing the cudf_collect_kwargs parameter from assert_gpu_result_equal, merging CPU/GPU kwargs logic, and deleting the assert_collect_raises helper. All test files are updated to use direct pytest.raises blocks for exception assertions.

Changes

Assertion helper refactor and test migration

Layer / File(s)	Summary
Assertion utilities refactoring python/cudf_polars/cudf_polars/testing/asserts.py	assert_gpu_result_equal removes cudf_collect_kwargs parameter; CPU kwargs are built by merging collect_kwargs with polars_collect_kwargs, GPU kwargs come from collect_kwargs alone. Private helper _process_kwargs and public helper assert_collect_raises are deleted.
Test migration to direct pytest.raises python/cudf_polars/tests/expressions/test_casting.py, test_datetime_basic.py, test_stringfunction.py, testing/test_asserts.py	Five test modules remove assert_collect_raises imports and replace each call with explicit pytest.raises(...) blocks around both q.collect() and q.collect(engine=pl.GPUEngine(...)) paths. The test_collect_assert_raises() test is removed.

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

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Possibly related PRs

• rapidsai/cudf#22493: Both PRs refactor asserts.py's assertion utilities and engine-related calling conventions in assert_gpu_result_equal.

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Suggested labels

non-breaking

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Suggested reviewers

• mroeschke

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 27.27% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: removal of legacy test scaffolding including assert_collect_raises and related keyword arguments.
Description check	✅ Passed	The description is directly related to the changeset, clearly explaining what is being removed and why.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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