Let's learn how to unit test your JavaScript with [Jest](http://facebook.github.io/jest), a JavaScript unit testing framework from Facebook. We'll install and optimize Jest for this project and see how quick and easy it is to get things going with Jest.

Test JavaScript with Jest

Jest comes pre-packaged with the ability to track code coverage for the modules you're testing, but it takes a little extra work to make it track untested files as well. Let's look at what Jest can do for you, what you have to do yourself, and how to setup code coverage thresholds so you can work to improving the code coverage numbers for your projects.

Track project code coverage with Jest

Jest ships with a pretty amazing interactive watch mode which you can initiate with `jest --watch`. Let's learn about the bits of interactivity and how this can really improve your workflow.

Use Jest's Interactive Watch Mode

Often when testing, you use the actual result to create your assertion and have to manually update it as you make changes to the feature. With Jest snapshot testing, you can let Jest do this part for you and write more tests and features faster and with more confidence. Let's learn about how you can use Jest snapshot testing to improve your own workflow.

Use Jest's Snapshot Testing Feature

Jest will default to utilize babel when your `node_modules` contains `babel-jest`. Depending on your environment this may already be the case! In this quick lesson, find out why that is and how to ensure that continues to work.

Add Babel Integration with Jest

React Storybook allows for easy snapshot testing integration with Facebook's Jest testing framework. Snapshot testing allows you to capture the state of your UI and then notify you when that UI has been altered. We can easily create and update snapshots with Storybook!
 




Jest

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