Introduction
Red-Green-Refactor loop
- Red: Write a test for a specific edge case (it fails because the feature isn’t built yet).
- Green: Write the bare minimum code to make that edge case pass.
- Refactor: Clean up the code while keeping all normal and edge-case tests passing
Benefits of TDD
- Better Code Quality: Forces simple, modular, and loosely-coupled design architectures.
- Early Bug Detection: Catches edge cases and functional defects immediately during creation.
- Living Documentation: Serves as a reliable, up-to-date specification of how the system behaves.
- Fearless Refactoring: Provides a safety net when changing or scaling legacy codebases.
Common Pitfalls
Typical individual mistakes include:
- Forgetting to run tests frequently
- writing too many tests at once
- writing tests that are too large or coarse-grained
- writing overly trivial tests, for instance omitting assertions
- writing tests for trivial code, for instance, accessors
Typical team pitfalls include:
- Partial adoption – only a few developers on the team use TDD
- poor maintenance of the test suite – most commonly leading to a test suite with a prohibitively long running time
- the abandoned test suite (i.e. seldom or never run) – sometimes as a result of poor maintenance, sometimes as a result of team turnover