test: fix vacuous registry-cleanup assertion in test_mode_registry

[arham766]

What does this PR do?

Type of change: Bug fix

Test-only fix (found writing #1915): test_mode_registry.py's final assertion compared the STRING 'test_registry' against registry OBJECTS in _all_registries — vacuously true regardless of behavior. It masked two real warts, now documented in-test: _ModeRegistryCls.del is unreachable (the class-level list holds a strong reference), and if a registry is removed from the list first, a later GC-triggered del raises ValueError from its unconditional list.remove (surfaced as PytestUnraisableExceptionWarning). The test now asserts the removed mode no longer resolves, cleans the registry from _all_registries explicitly, and checks residue by name — mutation-verified non-vacuous. The del warts may deserve a small source fix; happy to follow up.

Usage

N/A

Testing

Regression tests included, each verified to FAIL with the fix reverted. Combined battery with all sibling wave fixes: 381 passed across tests/unit/torch/opt, tests/unit/torch/utils, tests/unit/recipe, and quantization test_mode. Note: the unmerged suite PRs #1913-#1916 contain behavior-documenting NOTE tests pinning the OLD behavior fixed here — whichever lands second gets the NOTE tests flipped (happy to rebase either way).

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Additional Information

Issue: #1902 (wave-2 findings)

Summary by CodeRabbit

• Tests
  • Improved coverage for mode registration and removal behavior.
  • Verified removed modes are no longer available and missing lookups fail as expected.
  • Strengthened test cleanup to prevent leftover state between runs.

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📥 Commits

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• tests/unit/torch/opt/test_mode_registry.py

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📝 Walkthrough

Walkthrough

A test file for mode registry functionality was updated to import mock and pytest, add assertions verifying that a removed mode is no longer resolvable and raises KeyError, and rework test cleanup to explicitly remove registry instances and patch __del__ to avoid errors.

Changes

Test enhancement for mode registry

Layer / File(s)	Summary
Imports and strengthened test assertions/cleanup tests/unit/torch/opt/test_mode_registry.py	Adds mock and pytest imports; asserts removed mode is unresolvable via contained_in_any and that get_from_any raises KeyError; replaces del registry with explicit removal from _all_registries and patches __del__ to prevent cleanup exceptions.

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

🚥 Pre-merge checks | ✅ 6

✅ Passed checks (6 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the test-only fix to the vacuous registry-cleanup assertion in test_mode_registry.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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.
Security Anti-Patterns	✅ Passed	Only a unit test file changed; it contains no banned patterns like torch.load(weights_only=False), allow_pickle=True, trust_remote_code=True, eval/exec, or nosec.

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[arham766]

Consolidated into #1927 per maintainer feedback in #1902 — the suite was trimmed to only the lines codecov reports uncovered, with parametrization clusters deduplicated. Closing in favor of that PR.