Testing Fundamentals Review "If you can't test it, you don't understand it. Tests are proof of understanding." When to Apply Activate this skill when: - Reviewing test files ( .test.ts, .spec.ts, .test.js) - Junior asks about testing strategy - Completing a feature without tests - Discussing coverage or test quality --- The Testing Pyramid - Unit Tests (70%) : Fast, isolated, test one thing - Integration Tests (20%) : Components working together - E2E Tests (10%) : Critical user journeys only --- Stack-Specific Framework Guide | Stack | Unit/Integration | E2E | |-------|------------------|---…