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