Jest is a JavaScript testing framework designed to ensure correctness of any JavaScript codebase. It allows you to write tests with an approachable, familiar and feature-rich API that gives you results …

Jest can be used in projects that use webpack to manage assets, styles, and compilation. webpack does offer some unique challenges over other tools. Refer to the webpack guide to get started.

Note: babel-jest is automatically installed when installing Jest and will automatically transform files if a babel configuration exists in your project. To avoid this behavior, you can explicitly reset the …

Note: Jest documentation uses yarn commands, but npm will also work. You can compare yarn and npm commands in the yarn docs, here. Let's get started by writing a test for a hypothetical function that …

Jun 10, 2025 · If you'd like to learn how to build a testing framework like Jest from scratch, check out this video: There is also a written guide you can follow. It teaches the fundamental concepts of Jest and …

Browse the docs Find what you're looking for in our detailed documentation and guides. Learn how to get started with Jest. Troubleshoot problems with Jest. Learn how to configure Jest. Look at the full …

Jest is a universal testing platform, with the ability to adapt to any JavaScript library or framework. In this section, we'd like to link to community posts and articles about integrating Jest into popular JS libraries.

By now you should have a good idea of how Jest can help you test your applications. If you're interested in learning more, here's some related stuff you might want to check out.

See React: Function and Class Components. Reminders that with Class components, we expect Jest to be used to test props and not methods directly. Now let's use React's test renderer and Jest's …

Jest attempts to scan your dependency tree once (up-front) and cache it in order to ease some of the filesystem churn that needs to happen while running tests. This config option lets you customize …