CSS Modules are one of the most popular ways for styling React components. Whether you are using only CSS or a more advanced pre-processor like SASS, it doesn't matter for CSS Modules: You can write all these styles in your style sheet files next to your React components. Since we are building up on top of a custom React + Webpack application, it…

React Context is a powerful feature. If your React application grows in size beyond a small application, there is nothing wrong with giving it a try. Many third-party libraries like Redux are using it under the hood anyway, so why not learn about it. Especially if your component hierarchy grows in vertical size, it becomes tedious passing props…

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…