TEST: Reuse pct_change test inputs

[vyasr]

Description

Runs the existing period values against each input in one test item, reusing setup while preserving all 21 Series pct_change assertions.

Checklist

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

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📥 Commits

Reviewing files that changed from the base of the PR and between e78c254 and dd34418.

📒 Files selected for processing (1)

• python/cudf/cudf/tests/series/methods/test_pct_change.py

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📝 Summary

Summary by CodeRabbit

• Tests
  • Consolidated percentage-change test coverage to run multiple period values within a single test.
• Chores
  • Updated the SPDX copyright attribution to include NVIDIA CORPORATION & AFFILIATES.

Walkthrough

The percentage-change test updates its SPDX attribution and replaces pytest parameterization with a loop over -5, 0, and 5. Pandas comparisons and array-equality assertions remain unchanged.

Changes

Percentage-change test

Layer / File(s)	Summary
Test coverage refactor python/cudf/cudf/tests/series/methods/test_pct_change.py	The test loops over the supported periods values within one test function and updates the SPDX attribution.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~5 minutes

Suggested reviewers: galipremsagar, mroeschke

Merge Risk: ⚪ Minimal · up to dd344

No actionable merge-blocking risk remains; the test cleanup preserves the existing assertions.

🚥 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 1 functions across 1 files.	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 that the pct_change tests reuse setup while preserving all 21 assertions. It directly matches the changeset and PR objective.
Title check	✅ Passed	The title accurately identifies the main change: reusing pct_change test inputs. It is concise and specific.
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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🧪 Generate unit tests (beta)

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