test-driven-development

The red-green-refactor cycle in test-driven development requires writing a failing test first, implementing minimal code to pass it, and then refactoring. This enforces early requirement validation and guards against regressions throughout feature development.

To fix a bug using test-driven development, write a test that reproduces the exact bug first, then implement the code fix to make it pass. This guarantees regression protection by validating the fix against the specific failure condition.

To start writing tests before coding, write a failing test defining the intended feature change, then implement the minimal production code required to make that test pass. This ensures changes are well-validated and maintainable.

Test-driven development is applicable across small to large codebases. It drives software reliability by aligning behavior with expectations early, which is essential for managing complexity and preventing late-stage defects during feature development or refactoring.

Use test-driven development during refactoring to ensure minimal, well-factored production code without breaking existing functionality. The required failing tests validate changes early and provide continuous regression protection throughout the process.