E2E testing

While unit tests are isolated and independent by definition, end-to-end (or E2E) tests serve for, in a way, the opposite function: they intend to check the health of the system as a whole, and try to include as many components of the solution as possible. For this reason, in E2E tests we will focus on testing complete modules, rather than isolated components or controllers.

Preparation

Fortunately, we can use Jest for E2E testing just like we did for unit testing. We will only need to install the supertest npm package to perform API requests and assert their result. Let’s install it by running npm install --save-dev supertest in your console.

Also, we will create a folder called e2e in our project’s root folder. This folder will hold all of our E2E test files, as well as the configuration file for them.

This brings us to the next step: create a new jest-e2e.json file inside the e2e folder with the following contents:

{
  "moduleFileExtensions": ...