test-driven-development

What problem does it solve? Developers often write production code first and add tests afterward, which produces tests that pass immediately and prove nothing about correctness. This Skill enforces a strict test-first discipline so every feature and bugfix is verified by a failing test before any implementation exists. ## Core Features & Use Cases - Red-Green-Refactor Cycle: Guides writing a failing test, verifying it fails for the right reason, writing minimal code to pass, then 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 testing mock behavior, test-only methods in production classes, incomplete mocks, and mocking without understanding dependencies. - Use Case: When fixing a bug where empty emails are accepted, write a failing test asserting the rejection error, watch it fail, implement the minimal validation, and confirm all tests pass. ## 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.