Test-driven development

Use this skill ONLY when the user has opted into test-first development for the work at hand — they explicitly ask for TDD / test-driven / "write the test first" / red-green-refactor, OR they are starting a brand-new feature, module, or component and say they want it built test-driven. It guides the disciplined cycle: write a failing test, watch it fail for the right reason, write the minimal code to pass, refactor — and it pushes back on the rationalizations for skipping that order. Trigger on: "let's TDD this", "build X test-first", "write the tests first", "do this with red-green-refactor", "implement Y test-driven". Do NOT trigger on ordinary coding: every code edit, …