What is Jest?
Jest is an open JavaScript testing library from Facebook. Its slogan is "Delightful JavaScript Testing". While Jest can be used to test any JavaScript library, it shines when it comes to React and React Native.
Main Benefits
1) Developer Ready
Complete and ready to set-up JavaScript testing solution. Works out of the box for any React project.
2) Instant Feedback
Fast interactive watch mode runs only test files related to changed files and is optimized to give signal quickly.
3) Snapshot Testing
Capture snapshots of React trees or other serializable values to simplify testing and to analyze how state changes over time.
Jest is used by Facebook to test all JavaScript code including React applications. One of Jest's philosophies is to provide an integrated "zero-configuration" experience.
NPM and Yarn Command for Installation.
npm install --save-dev jest
yarn add --dev jest
Video for JEST Library
https://www.youtube.com/watch?v=7r4xVDI2vho