Too Long; Didn't Read
Jest is a great JavaScript testing framework by Facebook. It’s often used for testing React components, but is also a pretty good general purpose testing framework. Mocking API calls instead of testing with a real API is useful for a couple of reasons. It makes your tests ‘pure’, i.e. whether they fail or pass depends only on your code, and not on the data that the API returns. Using the official starter kit by Facebook, create-react-app. This comes with a working Jest configuration out of the box!