Category: Jest

Solution and explanation of the error "Cannot read properties of undefined (reading 'main')". Caused by Material UI incorrect Migration.

A basic overview of testing with Jest and React Testing Library. What are the differences between the two? How should they be used?

Sometimes when writing Jest unit tests you are going to want to be able to loop over items to quickly test different cases. Whether this be looping over an array of items, or counting between numbers in your Jest Test....

A walkthrough on how to mock local storage in Jest tests, as well as how to clear storage in jest tests. Example included.

How to mock es6 modules? Solution for how ES6 modules can be mocked in Jest unit tests. Mocking es6 modules with Jest.

Mocking date in Redux Toolkit slice with jest in unit tests solution. How to solve new date isostring issue in RTK mock.

How to use Arrange Act Assert pattern in unit testing, and why it is so helpful. Arrange-Act-Assert is powerful because it is simple. By keeping the tests short and concise means clean tests.

Solution for testing that images have rendered in React using Jest. And how to test an image alt and src in jest using React. Including example code.

How to mock a React component in a jest unit test. Example of how to mock a default or named component using React Testing Library.

Examples of how to use within in Jest and React Testing Library to target a specific section of the component. Restrict Jest queries to a particular element. Inside the context of a DOM node.