test-driven-development

Test-driven development is a test-first approach where you write a failing test, implement minimal production code to pass it, then refactor safely. This red-green-refactor cycle ensures every feature is guided by explicit expectations and verified before merging.

To write unit tests first, create a failing test for a small feature, run it to observe failure, implement just enough production code to pass, and run the tests again to confirm green. This enforces minimal code and prevents regressions.

Test-first development requires a mandatory failing test to prove the test checks actual behavior and the feature is genuinely needed. This prevents false positives and ensures production code is driven by explicit expectations rather than assumptions.

Yes, you can apply test-driven development for bug fixes and refactoring. Writing failing tests first documents expected behavior, guards against unintended changes, and ensures modifications do not introduce regressions before merging.

The best way to prevent regressions is adopting test-driven development. By maintaining a robust suite of tests that document intended behavior, you guard against unintended changes and ensure every feature implementation is verified.

You should not use a test-first approach when exploring unfamiliar APIs or writing throwaway prototypes where behavior is undefined. Test-driven development requires clear expected behavior to write meaningful failing tests before production code.