Fast interactive watch mode runs only test files related to changed files and is optimized to give signal quickly.
Capture snapshots of React trees or other serializable values to simplify UI testing and to analyze how state changes over time.
Zero configuration testing platform
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
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.
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!
Who's using Jest?
Jest is used by teams of all sizes to test web application, node.js services, mobile apps, and APIs.