Testing components

Testing components is important because this is what the user interacts with. Having automated tests on components gives us confidence that the app is working correctly and helps prevent regressions when we change code.

In this section, we will learn how to test components with Jest and React Testing Library. Then, we will create some tests on the checklist component we developed in the last chapter.

Understanding React Testing Library

React Testing Library is a popular companion library for testing React components. It provides functions to render components and then select internal elements. Those internal elements can then be checked using special matchers provided by another companion library called jest-dom.

A basic component test

Here’s an example of a component test:

test('should render heading when content specified', () => {
  render(<Heading>Some heading</Heading>);
  const heading =...