test-driven-development

Test-driven development is a test-first approach where you write a failing test, implement minimal production code to make it pass, then refactor for clarity. The red-green-refactor cycle enforces this by validating tests fail before code is written, pass after implementation, and maintain correctness during refactoring.

To write unit tests before features, start by writing a failing test that captures the desired behavior. Then implement the minimal production code required to make that test pass, ensuring your feature addition is validated through automated tests from the very beginning.

Yes, test-driven development is suitable for bug fixes and behavior changes. You write a failing test that reproduces the bug or captures the new expected behavior, then modify the production code to make the test pass, guarding against regressions.

Writing tests first prevents regressions, clarifies requirements before implementation, and increases confidence in code changes. This test-first mindset ensures code correctness is continuously validated through automated tests rather than being an afterthought.

While test-driven development enforces continuous quality assurance, it may introduce overhead for trivial changes or throwaway prototypes. If the desired behavior cannot be clearly defined as a failing test upfront, the test-first approach becomes less effective for ensuring code correctness.