Easy Setup
Easy Setup
Complete and easy to set-up JavaScript testing solution. Works out of the box for any React project.
Instant Feedback
Instant Feedback
Fast interactive watch mode runs only test files related to changed files and is optimized to give signal quickly.
Snapshot Testing
Snapshot Testing
Capture snapshots of React trees or other serializable values to simplify testing and to analyze how state changes over time.
Zero configuration testing platform
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. We observed that when engineers are provided with ready-to-use tools, they end up writing more tests, which in turn results in more stable and healthy code bases.
Fast and sandboxed
Fast and sandboxed
Jest parallelizes test runs across workers to maximize performance. Console messages are buffered and printed together with test results. Sandboxed test files and automatic global state resets for every test so no two tests conflict with each other.
Built-in code coverage reports
Built-in code coverage reports
Easily create code coverage reports using --coverage. No additional setup or libraries needed! Jest can collect code coverage information from entire projects, including untested files.
Zero configuration
Zero configuration
Jest is already configured when you use create-react-app or react-native init to create your React and React Native projects. Place your tests in a __tests__ folder, or name your test files with a .spec.js or .test.js extension. Whatever you prefer, Jest will find and run your tests.
Try it out!
You can try out a real version of Jest using repl.it. Consider a function, add(), that adds two numbers. We can use a basic test in add-test.js to verify that 1 + 2 equals 3. Hit "run" to try it out!
Powerful mocking library
Powerful mocking library
Powerful mocking library for functions and modules. Mock React Native components using jest-react-native.
Watch Talks about Jest
The Jest core team and contributors regularly speak about Jest and Delightful JavaScript Testing. Check out our talks about Building High-Quality JavaScript Tools at f8 2017 or our talk about Snapshot Testing at React Conf 2017.
Learn how to test JavaScript with
In this video by Kent C. Dodds you will learn how to install Jest and write your first unit test.
Who's using Jest?
Jest is used by teams of all sizes to test web applications, node.js services, mobile apps, and APIs.
