What problem does it solve? Code written before tests often ships with unverified behavior, hidden edge cases, and regressions discovered only in production. This Skill enforces a strict test-first discipline so every change is proven by a failing test before implementation begins. ## Core Features & Use Cases - Red-Green-Refactor Enforcement: Guides the full cycle of writing a failing test, verifying it fails for the right reason, writing minimal code to pass, and refactoring while staying green. - Rationalization Detection: Lists common excuses for skipping TDD ("too simple to test", "I'll test after") with concrete rebuttals and red flags that trigger a restart. - Testing Anti-Pattern Reference: Covers mock-behavior testing, test-only production methods, incomplete mocks, and over-mocking, with gate functions to catch each. - Use Case: When fixing a bug where negative session IDs are accepted, write a failing pytest case first, watch it fail, implement the validation, and confirm the suite stays green. ## Quick Start Use the test-driven-development skill to implement this feature by writing a failing test first, then the minimal code to make it pass.
