tdd

What problem does it solve? Writing tests after the fact often produces brittle, implementation-coupled tests that break on every refactor and fail to verify real behavior. This Skill enforces a disciplined red-green test-driven development loop so tests verify observable behavior through public interfaces and survive refactors. ## Core Features & Use Cases - Red-Green Loop Rules: Enforces writing a failing test first, then only the minimal code to pass it, one vertical slice at a time. - Seam Identification: Requires agreeing on public interface seams with the user before any test is written, focusing effort on critical paths. - Anti-Pattern Detection: Flags implementation-coupled, tautological, and horizontally-sliced tests, with examples of good and bad tests in tests.md and mocking guidance in mocking.md. - Use Case: When adding a checkout feature, ask the assistant to work test-first: it will confirm the seams with you, write one failing behavior test like "user can checkout with valid cart", implement the minimal code to pass, and repeat. ## Quick Start Ask the assistant to build the next feature or fix the bug using test-driven development, starting with one failing test at an agreed public seam.