Designing Tests

It gives you the full testing pyramid breakdown (70% unit, 20% integration, 10% E2E), framework recommendations across JavaScript, Python, and Go, and concrete templates for each test type following the arrange-act-assert pattern. The coverage thresholds are sensible (80% global, 95% for core modules), and the mock-versus-real guidance actually helps you avoid common pitfalls like mocking internal modules. Load it when you're setting up testing infrastructure from scratch or trying to hit coverage targets without writing garbage tests.