test-driven-development

Test-driven development guides software changes by enforcing a test-first workflow where you write a failing test before production code. It uses explicit fail and pass gates to ensure correctness during feature development, bug fixes, and refactoring.

The red-green-refactor cycle in unit testing involves writing a failing test, implementing minimal code to pass it, and refactoring while keeping tests green. This discipline maintains correct behavior and reduces defects.

To start writing tests before implementation, write a failing test for the desired behavior, then implement the minimal production code required to pass it. This ensures automated tests prove correctness before integration.

Yes, you can use test-driven development for bug fixes and refactoring. It enforces mandatory failing tests prior to code changes and applies strict verification gates to maintain correct behavior across any codebase relying on automated tests.

You should avoid a test-first workflow in codebases that do not rely on automated tests or lack strict verification gates. Without these explicit fail and pass gates, the mandatory failing test discipline cannot prove correctness effectively.