Read more about React

Snapshot tests are a common way to write lightweight component tests. When a snapshot test runs for the first time, it stores its output (e.g. rendered component's HTML structure) in a snapshot output file. Every time the snapshot test runs again, another snapshot output file…

If you are using Snapshot Tests with Jest for your components, there are a few pitfalls you have to be aware of. Two of them are very likely to apply to your written tests as well: 1) The output of snapshot tests becomes most often too large, if the actual snapshot test renders a…

Writing tests is an essential part of software development to ensure a robust application. Tests enable us to automatically verify that our application is working on a certain level. The certain level depends on the quality, quantity (coverage) and type of your tests (unit tests…

The following implementation shows you how to integrate Redux Persist into Next.js with a quick example. First, the installation of the library on the command line: Second, rather than having a straightforward function which creates our Redux store, we distinguish between…

Recommended alternative: Instead of Mocha/Chai, using Jest as test runner and assertion library for unit, integration and snapshot tests . Before setting up the test setup with different testing libraries and writing the React component tests, you will need a simple React…

Coveralls is used to show you the test coverage of your JavaScript application. Let's see how it can be used for your JavaScript project which is already on GitHub and connected to your Travis CI due to the previous CI setup tutorial. First, sign up at Coveralls.io with your…

End-to-end testing (E2E) was always a tedious task with testing frameworks from the past. However, nowadays many people are using Cypress.io for it. Their documentation has a high quality and their API is concise and clean. Let's use Cypress for this React testing tutorial…

In this React testing tutorial, we will introduce Enzyme in our Jest testing environment. Jest is commonly used as test runner -- to be able to run your test suites and test cases from the command line with optional configuration -- but also to make assertions in your test cases…

Jest got introduced by Facebook for testing JavaScript and especially React applications. It's one of the most popular ways to test React components nowadays. Since it comes with its own test runner, you can simply call Jest from the command line to run all your tests. All your…