Frontend Testing

Frontend testing is a core SDE-2 skill: interviews expect you to explain the testing pyramid, when to use unit vs integration vs E2E, and how tools like RTL, MSW, and Playwright fit together.

This module covers all test types with code examples, the 70/20/10 pyramid, snapshot testing trade-offs, performance measurement with Web Vitals, memory leak detection, and MSW for API mocking.

Good testing strategy balances speed and confidence: fast unit tests for logic, integration tests for component + API flows, and a thin layer of E2E tests for critical user journeys only.

Includes the 70/20/10 testing pyramid, RTL best practices, MSW for API mocking, Playwright login flows, snapshot testing pitfalls, Web Vitals measurement, and detecting memory leaks in React with DevTools.

Phase 10 (Weeks 10–12) of the interview roadmap. Senior Track spans modules 1–19; the Staff Track starts at module 20.