test-driven-development

Test-driven development writes a failing test first that specifies desired behavior, then implements minimal code to pass it. Start by defining what your feature should do in a test, run it to confirm failure, write just enough production code to pass, and refactor. This Red-Green-Refactor cycle ensures behavior aligns with requirements and prevents regression across new features, bug fixes, and refactoring.

Test-first development guides design decisions upfront, catches bugs earlier, and builds a safety net that reduces debugging time. Writing tests before implementation ensures your code satisfies requirements from the start and protects against regression as you refactor and add features.

Red-Green-Refactor applies whenever you add features, fix bugs, refactor existing code, or implement behavior changes. Write a failing test that specifies the intended behavior, confirm it fails, implement minimal code to pass, then refactor with confidence that tests catch regressions.

TDD builds a comprehensive safety net of tests that verify behavior continuously. By writing tests first, you catch misalignments between code and requirements immediately rather than discovering bugs late, and tests serve as executable documentation that guides future changes.

Yes. Test-driven development applies to refactoring by ensuring your changes preserve existing behavior while improving design. Write tests that capture current behavior, refactor with confidence, and use test failures to catch unintended side effects.