What problem does it solve?
It helps you avoid brittle, implementation-coupled tests by guiding you to write integration-style tests that specify observable behavior, then iterate through the red-green-refactor loop until the system works.
Core Features & Use Cases
- Behavior-first integration testing: Write tests that validate what the system does through public interfaces, not how it does it.
- Vertical slicing with tracer bullets: Use one test at a time (red → minimal green → refactor) to prevent “horizontal slicing” where test code outpaces real understanding.
- Refactoring-safe guidance: Keep tests resilient to internal changes so refactors improve structure without causing unnecessary test churn.
Use cases: Building new features, fixing bugs, and adding confidence to refactors in complex codebases where mocks and private-method assertions would create fragile coverage.
Quick Start
Use the tdd skill when you want to fix a bug or add a feature by writing one integration-style behavior test first, then implementing just enough to make it pass, repeating for the next behavior.