Using the Jest framework

Jest is a modern test framework that was authored by Facebook to fully leverage Node.js for running tests. It should have the power to run all the tests required at Facebook without requiring a diploma in engineering to understand, control, or modify it.

To use Jest, you need to install the jest package from npm:

$ npm install jest --save-dev

This allows you to use the jest command-line utility. Ideally, run it with npx as we did with the other tools:

$ npx jest

Jest can be configured by providing a jest.config.js file. The easiest way to create this kind of file is by using the jest tool with the --init flag. This will guide us through some questions to create a suitable configuration:

$ npx jest --init

The following questions will help Jest to create a suitable configuration for your project

 Would you like to use Jest when running "test" script in "package.json"? … yes

 Would you like to use Typescript for...