Configuring Jest with Next.js

Today, for software development, unit testing is extremely essential. In the Next.js development environment, Jest can be utilized as a popular unit testing framework for testing code. Jest provides us with the ability to easily write unit tests on our code and ensure that the software works correctly.

To get started with using Jest in Next.js, you first need to create a suitable environment for tests. This includes installing Jest and related plugins, configuring your project files, and writing initial tests. Proper installations allow your tests to run correctly and keep your code covered.

A major point when using Jest in Next.js projects is to consider the complexities related to the server execution environment and client. Since Next.js runs server-side applications, you should ensure that your tests cover all aspects of the code. For example, you may need to utilize tools like Enzyme or React Testing Library for testing React components.

In this guide, we will show you how to set up Jest for a Next.js project and write your initial tests. This includes recommendations for optimizing coverage code and also practical techniques for writing effective tests.

Installing and Configuring Jest

npm init -y
npm install --save-dev jest babel-jest @babel/preset-env @babel/preset-react react-test-renderer

mkdir __tests__

/* package.json */
{
  "scripts": {
    "test": "jest"
  },
  "jest": {
    "preset": "@babel/preset-env",
    "testEnvironment": "jsdom"
  }
}

/* babel.config.js */
module.exports = {
  presets: ["@babel/preset-env", "@babel/preset-react"]
};
    

npm init -y: Initializes the package.json file and facilitates initial setup.
npm install --save-dev jest babel-jest @babel/preset-env @babel/preset-react react-test-renderer: Installs the necessary packages for running jest and unit testing.
mkdir __tests__: Creates the __tests__ directory for storing test files.
package.json: Specifies configurations related to jest and the testing environment.
In the babel.config.js file: Babel presets for using modern JS and JSX in unit tests.