State in React is one of the most important topics when learning React . State breathes life into your React application. It's what makes your application grow beyond static content being displayed on a website, because a user can interact with it. Every interaction of a user with your application may change the underlying state which lead to…
Redux has been with us for a while now. What has gone public 2015 -- demonstrated by Dan Abramov in his infamous talk about time travel -- suddenly turned into many JavaScript developer's day to day business. Especially React developers were hit hard by this phenomenon, because it gave everyone a clear path on how to deal with state management…
React components connected to Redux can turn out pretty complex. Thus most people think that testing these complex components can turn out very complex as well. But it shouldn't be complex at all, if you take full control of the Redux store in your integration/unit test for the React component. I will use only Jest in this brief testing tutorial…
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 gets created; which is used to diff the output against the old snapshot…
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 component with lots of child components. This holds two problems in…
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, integration tests, snapshot tests, end-to-end tests (also called E2E…
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 server-side and client-side Redux store. In the case of the client-side…
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 application which can be tested in the first place. You will introduce a…
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 GitHub account. Second, synchronize your GitHub repositories and toggle…
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 series. First, you have to install it on the command line to your dev…
