Jest - JavaScript framework

Jest is a JavaScript testing framework maintained by Facebook, Inc. designed and built by Christoph Nakazawa with a focus on simplicity and support for large web applications. It works with projects using Babel, TypeScript, Node.js, React, Angular, Vue.js and Svelte.

zero config

Jest aims to work out of the box, config free, on most JavaScript projects.

snapshots

Make tests which keep track of large objects with ease. Snapshots live either alongside your tests, or embedded inline.

isolated

Tests are parallelized by running them in their own processes to maximize performance.

great api

From it to expect - Jest has the entire toolkit in one place. Well documented, well maintained, well good.

FAST AND SAFE

By ensuring your tests have unique global state, Jest can reliably run tests in parallel. To make things quick, Jest runs previously failed tests first and re-organizes runs based on how long test files take.

CODE COVERAGE

Generate code coverage by adding the flag --coverage. No additional setup needed. Jest can collect code coverage information from entire projects, including untested files.

EASY MOCKING

Jest uses a custom resolver for imports in your tests, making it simple to mock any object outside of your test’s scope. You can use mocked imports with the rich Mock Functions API to spy on function calls with readable test syntax.

GREAT EXCEPTIONS

Tests fail—when they do, Jest provides rich context why