What problem does it solve? Teams waste effort writing brittle tests that assert implementation details, over-mock internal components, and chase coverage numbers instead of real confidence. This Skill provides a clear testing philosophy so every test verifies user-visible behavior. ## Core Features & Use Cases - Two Users Principle: Ensures tests only observe what end users see or what developer consumers receive, eliminating third-user test-only code. - Testing Trophy Guidance: Prioritizes static analysis and integration tests over excessive unit or E2E tests, targeting roughly 70% meaningful coverage. - Mocking Boundaries: Defines exactly when mocking is acceptable (external APIs, network via MSW, file system, time) and when it destroys confidence. - Use Case: When reviewing a React test suite, apply the included good-vs-bad examples to rewrite tests that assert CSS classes or internal hook state into workflow-based integration tests. ## Quick Start Review my TypeScript test file and rewrite any tests that check implementation details into behavior-based integration tests.
