Today we're announcing a switch to major revisions for Jest with Jest 11.0 being the first major release. Jest has been used by Facebook engineers and on our continuous integration systems for years and we believe Jest has been way beyond a “1.0 release” for a long time. This is similar to a change the React team has made.

If you are using Jest 0.9 or Jest 0.10 the upgrade should be seamless. All changes from the last few months were rolled into Jest 11.0.

New in Jest 11.0​

Babel Integration and Simplified Setup​

babel-jest was adopted within the newly modularized Jest repository and it is now seamlessly integrated into Jest. If you are upgrading from an older version of Jest or are looking to adopt Jest, we recommend reading the Getting Started guide.

Jest is running thousands of tests at Facebook at all times, either through continuous integration or invoked by engineers manually during development. This worked well for years even as the people working on Jest moved on to other projects within Facebook.

As engineers added more and more tests though, we noticed the performance of Jest wasn't going to scale. Additionally, in the last year the JavaScript ecosystem has changed dramatically with the introduction of things like npm3 and Babel, which we hadn't anticipated. We formed a new Jest team to address all of these issues and we'll be sharing our progress and plans on this blog from now on.