Excercise assert_collect_raises with engine fixture

[mroeschke]

Description

The pattern that was replaced in #22535 would only test that collection errors were raised with the in-memory engine.

As apart of #22346, we should ensure that our other engines also exhibit a collection error.

Also checks if tests that were skipped in #21828 no longer segfault

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[coderabbitai]

📝 Walkthrough

Walkthrough

The PR updates test assertions and execution patterns across four test modules to standardize behavior when running under streaming versus non-streaming GPU engines. Boolean and string tests that were previously skipped on streaming engines are now enabled, while casting and string validation tests are updated to branch error assertions based on engine type.

Changes

Test execution parity across engine types

Layer / File(s)	Summary
Remove skip guards to enable tests on streaming engines python/cudf_polars/tests/expressions/test_booleanfunction.py, python/cudf_polars/tests/expressions/test_stringfunction.py	is_streaming_engine import is removed from boolean tests and skip guards are deleted from test_boolean_function_unary and test_boolean_horizontal, allowing them to run on streaming engines. String pad test skip guard is also removed to enable execution on streaming engines.
Branch error assertions based on engine type python/cudf_polars/tests/expressions/test_casting.py, python/cudf_polars/tests/expressions/test_stringfunction.py	Tests are updated to use pytest.RaisesGroup for streaming engines and pytest.raises for non-streaming engines when asserting collection errors. Changes apply to casting strict-mode tests and string function validation (to_datetime, string_to_numeric_invalid, string_zfill_forbidden_chars).
Standardize engine fixture usage in collection calls python/cudf_polars/tests/expressions/test_datetime_basic.py, python/cudf_polars/tests/expressions/test_stringfunction.py	Tests are modified to use the provided engine fixture parameter during collection instead of constructing explicit in-memory engines, ensuring consistent engine invocation in error paths.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• rapidsai/cudf#22535: Related changes to exception assertion patterns in the same test files, replacing assert_collect_raises with explicit pytest.raises for collection error paths.

Suggested labels

Python, cudf-polars

Suggested reviewers

• vyasr
• nirandaperera

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% 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
Description check	✅ Passed	The description clearly explains the motivation for the changes: ensuring collection errors are tested with multiple engines (not just in-memory), referencing related issues, and verifying previously skipped tests no longer segfault.
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.
Title check	✅ Passed	The title mentions 'assert_collect_raises with engine fixture', which directly corresponds to the main objective of modifying tests to use the engine fixture instead of the in-memory engine for testing collection error behavior across different engines.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@python/cudf_polars/tests/expressions/test_stringfunction.py`:
- Line 595: Wrap the engine-backed call q.collect(engine=engine) in the same
pytest.raises(...) assertion used for the non-engine negative `fill` path so the
test verifies the expected exception for engine execution; locate the test that
exercises `q` and `engine`, replace the bare q.collect(engine=engine) with a
with pytest.raises(ExpectedError): q.collect(engine=engine) (use the same
exception type/class used elsewhere in this test file for the negative `fill`
path).

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: d0f423c9-991c-4700-ac61-de60cba6ef2f

📥 Commits

Reviewing files that changed from the base of the PR and between f239649 and e35c88d.

📒 Files selected for processing (4)

• python/cudf_polars/tests/expressions/test_booleanfunction.py
• python/cudf_polars/tests/expressions/test_casting.py
• python/cudf_polars/tests/expressions/test_datetime_basic.py
• python/cudf_polars/tests/expressions/test_stringfunction.py

💤 Files with no reviewable changes (1)

• python/cudf_polars/tests/expressions/test_booleanfunction.py

[mroeschke]

/merge