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Fix Failing or Flaky Tests

Domain: Engineering - Core | Skill: fix | Source: engineering-team/playwright-pro/skills/fix/SKILL.md

Fix Failing or Flaky Tests

Diagnose and fix a Playwright test that fails or passes intermittently using a systematic taxonomy.

Input

$ARGUMENTS contains: - A test file path: e2e/login.spec.ts - A test name: ""should redirect after login"- A description:"the checkout test fails in CI but passes locally"`

Steps

1. Reproduce the Failure

Run the test to capture the error:

npx playwright test <file> --reporter=list

If the test passes, it's likely flaky. Run burn-in:

npx playwright test <file> --repeat-each=10 --reporter=list

If it still passes, try with parallel workers:

npx playwright test --fully-parallel --workers=4 --repeat-each=5

2. Capture Trace

Run with full tracing:

npx playwright test <file> --trace=on --retries=0

Read the trace output. Use /debug to analyze trace files if available.

3. Categorize the Failure

Load flaky-taxonomy.md from this skill directory.

Every failing test falls into one of four categories:

Category Symptom Diagnosis
Timing/Async Fails intermittently everywhere --repeat-each=20 reproduces locally
Test Isolation Fails in suite, passes alone --workers=1 --grep "test name" passes
Environment Fails in CI, passes locally Compare CI vs local screenshots/traces
Infrastructure Random, no pattern Error references browser internals

4. Apply Targeted Fix

Timing/Async: - Replace waitForTimeout() with web-first assertions - Add await to missing Playwright calls - Wait for specific network responses before asserting - Use toBeVisible() before interacting with elements

Test Isolation: - Remove shared mutable state between tests - Create test data per-test via API or fixtures - Use unique identifiers (timestamps, random strings) for test data - Check for database state leaks

Environment: - Match viewport sizes between local and CI - Account for font rendering differences in screenshots - Use docker locally to match CI environment - Check for timezone-dependent assertions

Infrastructure: - Increase timeout for slow CI runners - Add retries in CI config (retries: 2) - Check for browser OOM (reduce parallel workers) - Ensure browser dependencies are installed

5. Verify the Fix

Run the test 10 times to confirm stability:

npx playwright test <file> --repeat-each=10 --reporter=list

All 10 must pass. If any fail, go back to step 3.

6. Prevent Recurrence

Suggest: - Add to CI with retries: 2 if not already - Enable trace: 'on-first-retry' in config - Add the fix pattern to project's test conventions doc

Output

  • Root cause category and specific issue
  • The fix applied (with diff)
  • Verification result (10/10 passes)
  • Prevention recommendation