test-driven-development

Drives implementation test-first through red-green-refactor cycles, including multi-unit features built outside-in, legacy code without tests, and sessions that keep a written cycle log. Use when building a new behavior, when asked to fix a bug, or when changing what existing code does, and applies even when the code is pasted inline and the request does not mention tests. Also use whenever the request mentions TDD, test-first, red-green-refactor, or reproducing a bug with a failing test before fixing it, and when implementation keeps landing before anyone knows how it will be verified. For one small behavior or bug fix, test-driven-development-quick is enough; for tests added after the code exists, use writing-unit-tests.