testing-obsessivelisted

# Testing Foundations Comprehensive testing guidance for JavaScript/TypeScript applications, with emphasis on Vitest, Svelte component testing, and pragmatic test-after development. Addresses testing as a professional skill for portfolio evidence and code quality. ## When This Skill Applies Use this skill when: - Writing new tests for features or components - Setting up testing infrastructure - Debugging failing tests - Discussing testing strategies or coverage goals - Refactoring tests for better maintainability - Questions about testing best practices - Deciding what to test and when ## Testing Philosophy ### Why Test? **Not for 100% coverage** - Test for: 1. **Confidence** - Deploy without fear 2. **Documentation** - Tests show how code should be used 3. **Refactoring safety** - Change implementation without breaking behaviour 4. **Regression prevention** - Bugs stay fixed 5. **Design feedback** - Hard-to-test code often signals design issues ### The Testing Pyramid ``` /\ / \ E2E Tests / \ (Few, slow, expensive) /------\ / \ Integration Tests / \ (Some, medium speed) /------------\ / \ Unit Tests ---------------- (Many, fast, cheap) ``` **Distribution target**: - **70%** Unit tests - Fast, isolated, test single functions/modules - **20%** Integration tests - Test component interactions, API calls - **10%** E2E tests - Test critical user journeys ### Pragmatic Approach **Test-after development