What is Jest and how is it used with React?

Short answer: Jest is a JavaScript testing framework created by Facebook, commonly used for testing React applications. It comes with: Test runner: Executes test files. Assertions: Provides functions like expect() for asserting conditions. Mocks: Mocking capabilities for API calls or functions. Snapshots: Captures UI output at a given time. How to use Jest with React: Install Jest: npm install --save-dev jest

Real-world example (ShopNest)

ShopNest’s storefront is React: components for ProductCard, CartDrawer, and CheckoutForm, with hooks for local UI state.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.