Testing Patterns & Strategies Comprehensive guide to testing JavaScript/TypeScript applications. Complements the skill (which focuses on workflow) by providing concrete patterns, strategies, and anti-patterns. When to Use This Skill Activate when the user: - Wants to write tests for existing or new code - Needs to establish a testing strategy for a project - Wants to improve test coverage or reliability - Has flaky or brittle tests - Asks about mocking, stubbing, or test doubles - Needs guidance on unit vs integration vs E2E tests Testing Pyramid Rule of thumb: 70% unit, 20% integration, 10%…