TDD

Output language: answer and write artifacts in the user's own language (match their messages, not the repo's history).

Overview

Write the test first. Watch it fail. Write the minimal code to pass. Refactor.

Core principle: if you didn't watch the test fail, you don't know it tests the right thing.

REQUIRED COMPANION: use test-design for what to feed, assert, and mock. This skill is only the rhythm. Formalistic RED tests are still forbidden — a failing theater test proves nothing.

When to Use

Always: new features, bug fixes, refactoring, behavior changes.

Exceptions (ask the human first): throwaway prototypes, generated code, pure config with no behavior.

Thinking "skip TDD just this once"? Stop — that's rationalization.