test: deflake TestCompareDynamic_ZeroAllocHotPath

[matthyx]

Summary

TestCompareDynamic_ZeroAllocHotPath (pkg/registry/file/dynamicpathdetector/tests) is flaky. It was the cause of the intermittent pr-created / test failures (e.g. on #339, which is unrelated — it only touches summary-storage aggregation).

Root cause

The test measured allocations by diffing the process-global runtime.MemStats.Mallocs counter around a 10,000-iteration loop:

runtime.ReadMemStats(&before)
for i := 0; i < iters; i++ { _ = CompareDynamic(...) }
runtime.ReadMemStats(&after)
require.Equal(t, uint64(0), after.Mallocs-before.Mallocs)

Mallocs is process-wide, so a single allocation from a background runtime goroutine (GC assist, sysmon, the testing timer) landing inside the measurement window flips the delta to 1 and fails the assertion. The microsecond-scale window makes it rare but nonzero — the failure was observed flipping between different subtests across runs (literal_mismatch in CI, literal_exact_match locally), the signature of a flake rather than a regression.

Fix

Switch to testing.AllocsPerRun, which pins GOMAXPROCS(1) during measurement and integer-divides total mallocs by the run count. A stray sub-runs allocation now floors to 0 instead of flaking, while a genuine per-call allocation still yields ~1.0 and fails the zero-alloc contract. The contract is preserved; only the noise is removed.

Verification

• 30/30 isolated runs green (previously ~PASS/PASS/FAIL/FAIL/PASS).
• Full go test ./... suite green.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Tests
  • Updated a performance-oriented test to use a more reliable allocation check.
  • The zero-allocation assertion now uses per-run allocation measurement with clearer failure messaging.

[coderabbitai]

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 49afe880-3669-45ae-995e-d4c9e76fcf81

📥 Commits

Reviewing files that changed from the base of the PR and between aa63382 and aabb0a8.

📒 Files selected for processing (1)

• pkg/registry/file/dynamicpathdetector/tests/compare_dynamic_memoise_test.go

📝 Walkthrough

Walkthrough

The hot-path allocation check in one test was rewritten to use testing.AllocsPerRun with a zero-allocation assertion instead of comparing runtime.MemStats before and after repeated iterations.

Changes

Hot-path allocation test

Layer / File(s)	Summary
Allocation assertion rewrite pkg/registry/file/dynamicpathdetector/tests/compare_dynamic_memoise_test.go	TestCompareDynamic_ZeroAllocHotPath now measures allocations with testing.AllocsPerRun and asserts zero allocations with require.Zerof.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Poem

A bunny peeks at the hot-path run,
AllocsPerRun makes the counting fun.
No malloc crumbs in the meadow stay,
just zero hops and a tidy test today.
🐇✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 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 main change: deflaking the TestCompareDynamic_ZeroAllocHotPath test.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
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.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/deflake-zeroalloc-hotpath

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[github-actions]

Summary:

• License scan: failure
• Credentials scan: failure
• Vulnerabilities scan: failure
• Unit test: success
• Go linting: failure