This is a comprehensive testing guide for React, Next.js, and NestJS stacks that actually gives you the ratios (70% unit, 20% integration, 10% E2E) and concrete coverage targets instead of vague advice. It covers the full spectrum from Jest/Vitest unit tests through Supertest integration tests to Playwright E2E, with the AAA pattern and test organization examples baked in. The skill checks your project's existing patterns first, which is smart since every codebase has its own testing quirks. If you're setting up testing infrastructure from scratch or trying to standardize practices across a full stack TypeScript project, this gives you the opinionated structure most teams eventually land on anyway.
npx skills add https://github.com/shipshitdev/library --skill testing-expert