test-driven-development

What problem does it solve? Code written before tests often ships with unverified behavior, hidden bugs, and no proof that tests actually catch failures. This Skill enforces a strict test-first discipline so every line of production code is backed by a test that was watched failing first. ## Core Features & Use Cases - Red-Green-Refactor Cycle: Guides the agent through writing a failing test, verifying the failure, writing minimal passing code, and refactoring safely. - Rationalization Blocking: Explicitly counters common excuses like "I'll test after" or "too simple to test" with concrete rebuttals and red-flag stop conditions. - Test Quality Rules: A companion reference (writing-good-tests.md) defines how to name the break each test catches, avoid mock assertions, and run mutation checks. - Use Case: When asked to fix a bug where empty emails are accepted, the agent first writes a failing test asserting the rejection, watches it fail, then implements the minimal validation fix. ## Quick Start Ask the agent to implement a new feature or bugfix using test-driven development with a failing test written first.