Flaky Test Detector Skill
A Claude Code skill for detecting flaky test patterns that cause intermittent CI failures.
Trigger Phrases
This skill activates when you mention:
- "flaky test"
- "intermittent failure"
- "test sometimes fails"
- "race condition in test"
- "timing issue in test"
- "test passes locally but fails in CI"
- "non-deterministic test"
Capabilities
Pattern Detection
Scans *.test.ts and *.spec.ts files to detect:
| Severity | Pattern | Risk |
|---|---|---|
| HIGH | ttl.*:\s*1\b | 1-second TTL causes second-boundary race conditions |
| HIGH | Math.floor(Date.now() / 1000) | Second truncation creates timing edge cases |
| HIGH | setTimeout([^,]+,\s*\d{1,2}) | Very short timeouts (<100ms) are unreliable |
| MEDIUM | Date.now() without mocking | Real time in tests causes non-determinism |
| MEDIUM | timeout.*:\s*[1-9]0?\b | Low timeout values cause race conditions |
| MEDIUM | new Date() without mocking | Real date in tests causes flakiness |
| LOW | Math.random() without seeding | Random values cause non-determinism |
| LOW | process.nextTick in assertions | Timing-dependent assertions |
Context Extraction
For each detected pattern, the skill extracts:
- File path and line number
- Surrounding code context (3 lines before/after)
- Pattern severity classification
- Specific risk explanation
Fix Suggestions
Generates actionable fix suggestions:
vi.useFakeTimers()for time-based flakiness- TTL increase recommendations
- Mock injection patterns
- Deterministic alternatives
Usage
Scan Current Directory
# Run the detector on all test files
npx tsx scripts/index.ts
# Scan specific directory
npx tsx scripts/index.ts ./src/tests
# Output as JSON
npx tsx scripts/index.ts --json
Integration with CI
Add to your CI pipeline to catch flaky patterns before merge:
- name: Check for flaky test patterns
run: npx tsx scripts/index.ts --ci