Update jest.md

radar/2017-03-01/jest.md

@@ -1,6 +1,18 @@
 ---
 title:      "Jest"
-ring:       trial
+ring:       adopt
 quadrant:   tools
 
----
+---
+[Jest](https://facebook.github.io/jest/) is a javascript testing framework by facebook to test javascript code **and** react applications / components.
+
+We started using Jest (and [watchmen](https://github.com/facebook/watchman)) 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](https://medium.com/@RubenOostinga/combining-chai-and-jest-matchers-d12d1ffd0303#.3callo273), chai and jest test matchers work fine together.