test-driven-development

Test-driven development is a practice of writing failing tests before implementation to enforce a red-green-refactor cycle, ensuring code changes are minimal and behavior is verified before refactoring.

To prevent regressions, write a failing test that defines expected behavior first, then implement just enough code to pass it, and finally clean up the code while ensuring the test stays green.

Test-driven development requires a testing framework to execute the red-green-refactor cycle, but it does not mandate a specific tool, making it broadly applicable across software projects.

Test-driven development is useful for feature development, bug fixes, and refactors across projects, encoding intended usage and edge cases into behavioral documentation whenever verifying behavior is essential.

Writing failing tests first prevents guessing by defining a clear behavioral contract upfront, which guides implementation and prevents regressions that often occur when coding without defined expectations.