What problem does it solve? Writing tests after code often produces brittle, implementation-coupled tests that break on refactors and fail to verify real behavior. This Skill enforces a disciplined red-green TDD loop so tests verify behavior through public interfaces and survive refactoring. ## Core Features & Use Cases - Red-Green Loop Rules: Enforces writing a failing test first, then only enough code to pass it, one vertical slice at a time. - Seam-Based Test Design: Requires agreeing on public interface seams with the user before any test is written, focusing effort on critical paths. - Anti-Pattern Detection: Identifies implementation-coupled, tautological, and horizontally-sliced tests, with mocking guidelines for system boundaries only. - Use Case: When adding a checkout feature, use this Skill to define the public seams, write one failing behavior test ("user can checkout with valid cart"), implement the minimal code to pass, and repeat slice by slice. ## Quick Start Use the tdd skill to build this feature test-first, starting by agreeing on the public seams we should test.
