TechradarDev/radar/2017-03-01/jest.md

title, ring, quadrant, tags

title	ring	quadrant	tags
Jest	assess	tools	frontend quality assurance

Jest is a JavaScript testing framework by facebook to test JavaScript code and React applications / components.

We started using Jest (and watchmen) instead of Karma because it:

• gives us integrated mocking library
• gives us integrated support for testing "promises"
• gives us integrated code coverage report
• automatically runs tests related to changed files (instead of all tests)
• gives us parallel test execution
• gives us snapshot testing for React components

It is easy to set up. And even if you have a running setup with Karma/Chai you can easily replace Karma with Jest. With a small workaround, Chai and Jest test matchers work fine together.