test-driven-development

Test-driven development is a test-first workflow where you write a minimal failing test, implement the smallest code change to pass it, then refactor while keeping tests green. This red-green-refactor loop defines expected behavior and catches regressions early.

To start writing tests first, write a focused failing test describing the desired behavior, run it to confirm it fails for the right reason, implement minimal code to pass, and refactor while keeping all tests green throughout the process.

You should avoid test-first development for throwaway prototypes or generated and config files without human guidance. It is best suited for feature development, bug fixes, refactoring, and behavior changes where automated tests validate outcomes.

Yes, test-driven development prevents regressions during refactoring by enforcing that automated tests validate outcomes. You write minimal failing tests to specify behavior before implementation, ensuring changes remain safe and tests stay green through refactoring.

The best way to define expected behavior before implementation is writing a minimal, focused failing test that captures the intended behavior. This test-first approach prevents ambiguous requirements and costly debugging later in the development cycle.