Flaky Tests

November 9, 2023

What are Flaky Tests?

Flaky tests are defined as tests that return both passes and failures despite no changes to the code or the test itself.

Common Causes

  • Asynchronous operations
  • Time dependencies
  • Shared state between tests
  • Race conditions
  • Network reliability
  • Resource constraints

Impact on Development

  • Reduced confidence in test suite
  • Increased build times
  • Developer frustration
  • Delayed releases
  • Technical debt

Solutions

Problem Solution
Async Issues Implement proper wait mechanisms
Timing Problems Use deterministic time controls
Shared State Isolate test environments
Race Conditions Implement proper synchronization

Best Practices

  1. Isolate tests properly
  2. Use deterministic data
  3. Implement retry mechanisms
  4. Monitor test execution times
  5. Document known flaky tests
  6. Set up proper test environments

Detection Strategies

  • Run tests multiple times
  • Use test analytics tools
  • Monitor test execution history
  • Implement logging for failures

Prevention Tips

  • Write deterministic tests
  • Avoid external dependencies when possible
  • Use proper mocking techniques
  • Implement proper cleanup routines
  • Regular test maintenance
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