Introduction and background

ReactJs is a very popular open-source JavaScript library that is used for front-end development. It is extremely flexible and user-friendly, which makes it easy for developers to play around with state and props in React Components. This, in turn, helps to make the app more attractive and interactive.

React is maintained by Facebook, along with a worldwide community of companies and individual developers. It is great for fetching data that changes rapidly and which needs to be recorded and is therefore used as a base in the development of mobile apps and single-page applications.

In simple words, React allows developers to create web applications that are capable of changing data without having to reload the page. The main advantages that React offers include ease of use, simplicity, and scalability. It is also very fast, making it highly efficient.

Challenge

When developers work on a React app, they often play with state and props to make their apps more interactive and appealing. During development, everything may seem to work fine, but in many cases, the app faces issues once it is rolled out into the market when it is used by real people in the real world. This is because, oftentimes, some of the use cases of the app fail.

When you develop a web application, and you don’t run any test, it means that the beta testers will be the users in the real world, which is extremely risky. Besides, if your app fails, you cannot blame others for not trusting an untested code.

Unit testing of apps is required for the following reasons –

• To ensure that each part of the program is correct individually.
• To check out input validation logic and data transformation.
• To check any isolated operation.
• It helps in writing a test-driven approach.
• Make sure the right things render when they are meant to.

Solution

To carry out efficient and reliable unit testing, Jest and Enzyme are required. Jest is a JavaScript testing framework that is developed by Facebook, with its main advantage being that it is very easy to use while being fast and safe. Code coverage, great expectations, snapshots, and easy mocking are other benefits. Create React App is then shipped with a ready-to-use Jest setup.

The Enzyme is a JavaScript testing utility for React, which can be used for easily asserting, manipulating, and traversing the output of your React Component. It was created by Airbnb and is quite popular since it adds several additional utility methods that are used for rendering a component(s), as well as finding and interacting with elements.

So, Jest is used as the test runner, assertion library, and mocking library, while Enzyme is used to provide additional testing utilities to interact with elements.