Troubleshooting

[sudoUgando]

A workflow step that runs npm test is failing intermittently — passing on some runs, failing on others, with no code changes in between. What's the first thing you should check, and how would you modify the workflow to get more reliable debugging information?

[EimanTahir027]

A workflow step that runs npm test is failing intermittently — passing on some runs, failing on others, with no code changes in between. What's the first thing you should check, and how would you modify the workflow to get more reliable debugging information?

This is a classic flaky test scenario. Here's what I'd do:

First thing to check

Look at exactly which tests are failing — are they always the same tests, or different ones each time? Flaky tests that consistently fail on the same test usually indicate a test-specific issue (timing, async, state leakage, or ordering dependency), while random failures across different tests suggest a broader infrastructure issue (resource contention, parallelism problems).

Check for common patterns:

• Test ordering dependency — does a test pass when run alone with --test-name-pattern but fail in a full suite?
• Timing/async issues — missing await, insufficient timeouts, race conditions
• Shared mutable state — tests modifying globals, files, or databases without cleanup

How to modify the workflow for better debugging

Add these to your workflow configuration:

# 1. Retry failed tests automatically to distinguish flakes from real failures
- name: Run tests with retry
  run: npm test -- --retries 2
  # or for Jest: --jest --retryTimes=2

# 2. Run in single-threaded mode on retry to isolate ordering issues
- name: Re-run failed tests sequentially
  if: failure()
  run: npm test -- --runInBand --test-path-pattern="$(...)" 

# 3. Collect and upload artifacts when tests fail
- name: Upload test artifacts
  if: failure()
  uses: actions/upload-artifact@v4
  with:
    name: test-results
    path: |
      test-results/
      test-report.html

# 4. Set CI=true for cleaner failure output
env:
  CI: true

The most valuable single change: add --shard or --partition to run tests in smaller batches, so you can pinpoint whether the flakiness is proportional to load or specific to certain test groupings.