How to fall in love with TDD - Gui Ferreira - NDC Oslo 2024

TDD works like a flywheel - hard to start but builds momentum over time. Initial investment pays off as confidence and speed increase

Key challenges in TDD adoption:

• Writing tests first feels unnatural initially
• Maintaining test quality and avoiding fragile tests
• Choosing right test scope and avoiding overuse of mocks
• Keeping test execution time manageable
• Getting team buy-in and overcoming resistance

Focus on testing behaviors rather than implementation details:

• Test through public contracts/interfaces
• Avoid coupling tests to internal structure
• Allow internal refactoring without breaking tests
• Use real collaborators instead of mocks when possible

TDD Best Practices:

• Start with a test list to capture requirements and cases
• Take small steps, don’t try to solve everything at once
• Run tests frequently to catch issues early
• Refactor after getting tests to pass
• Keep test code clean and maintainable

Benefits of proper TDD:

• Reduced debugging time
• Better design through incremental development
• Documentation through tests
• Increased confidence in changes
• Faster feedback cycles

Testing Strategy:

• Unit test the core domain logic
• Integration test external boundaries
• Create stable contracts between components
• Use acceptance tests sparingly for critical flows
• Target 90%+ coverage but don’t make it the goal

Mindset changes needed:

• Think about design before implementation
• Embrace incremental development
• Accept initial productivity hit for long-term gains
• Focus on value of tests, not just coverage
• Have empathy for team members learning TDD

Tools and techniques:

• Use mutation testing to verify test quality
• Keep test execution time under 60 seconds
• Leverage architecture patterns that enable testing
• Write test lists before implementation
• Practice refactoring to keep code clean