TEST: Remove deterministic temporal and rolling skips

[vyasr]

Description

Replace temporal, reduction, and rolling parameter combinations that deterministically skipped before an assertion with their existing supported subsets. Every combination that previously ran, including its expected failures and warning checks, still runs. The rolling variance/std inputs are additionally module-scoped and read-only, so option variants reuse identical data rather than reconstructing it.

Checklist

• I am familiar with the CONTRIBUTING.md guidelines.
• New or existing tests cover these test-only changes.
• Documentation updates are not needed.

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📥 Commits

Reviewing files that changed from the base of the PR and between a8ad204 and 8c1e3f3.

📒 Files selected for processing (4)

• python/cudf/cudf/tests/indexes/timedeltaindex/test_binops.py
• python/cudf/cudf/tests/series/methods/test_reductions.py
• python/cudf/cudf/tests/series/test_binops.py
• python/cudf/cudf/tests/window/test_rolling.py

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📝 Summary

Summary by CodeRabbit

• Tests
  • Expanded and clarified coverage for supported timedelta arithmetic and datetime/timedelta reductions.
  • Improved validation of rolling-window operations, including statistical reductions and grouped rolling calculations.
  • Reduced ambiguous test behavior by explicitly covering supported operation combinations and valid window configurations.
  • Reused consistent datasets across rolling statistical tests to improve coverage reliability and consistency.

Walkthrough

The test suite now parameterizes supported timedelta, datetime, and rolling operations explicitly. Runtime skips for unsupported operations and invalid rolling combinations were removed. Rolling variance and standard deviation tests reuse module-scoped fixtures.

Changes

Supported operation test coverage

Layer / File(s)	Summary
Arithmetic and reduction coverage python/cudf/cudf/tests/indexes/timedeltaindex/test_binops.py, python/cudf/cudf/tests/series/test_binops.py, python/cudf/cudf/tests/series/methods/test_reductions.py	Timedelta arithmetic and datetime/timedelta reduction tests now use explicit supported-operation lists instead of runtime skip branches.
Rolling reduction fixtures python/cudf/cudf/tests/window/test_rolling.py	Rolling tests define supported reductions and reuse module-scoped window-size and generated-data fixtures for large variance and standard deviation cases.
Valid rolling parameter combinations python/cudf/cudf/tests/window/test_rolling.py	Groupby rolling UDF tests generate only combinations where min_periods is less than or equal to window_size.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 8c1e3

This updates test collection to run supported temporal and rolling cases directly while reusing deterministic rolling inputs. No current merge-blocking risk remains.

Suggested reviewers: galipremsagar, matt711

🚥 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%. Docstring coverage is scoped to functions touched by this diff. Analyzed 14 functions across 4 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
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 clearly and concisely describes the main change: removing deterministic skips from temporal and rolling tests.
Description check	✅ Passed	The description accurately explains the test parameter filtering, preservation of runnable cases, rolling fixture reuse, and validation performed.

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✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

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[vyasr]

/ok to test

[vyasr]

/ok to test

[bdice]

Approving but not merging, see comment.

[bdice]

The negative filter with explicit skips made it easier to see gaps in functionality. Not a blocker, just raising that for awareness.