Adding Testing to Next.js Applications: A Guide to Incorporating Unit Test

In this section, we will guide you through the process of enhancing your Next.js application's quality by adding unit and integration tests. We will use testing libraries such as Jest and Testing Library to ensure the reliability and functionality of your application.

Unit Testing with Jest

Jest is a popular testing library for performing unit tests in JavaScript applications. Here's how you can add unit tests to your Next.js application using Jest:

Install Jest and related libraries:

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

Create a Jest configuration file (jest.config.js):

module.exports = {
  testEnvironment: 'jsdom',
  transform: {
    '^.+\\.jsx?$': 'babel-jest',
  },
};

Write unit tests using Jest:

import { sum } from './utils';

test('adds 1 + 2 to equal 3', () => {
  expect(sum(1, 2)).toBe(3);
});

Integration Testing with Testing Library

Testing Library is a powerful toolkit for testing user interactions in applications. Here's how you can add integration tests to your Next.js application using Testing Library:

Install Testing Library and related libraries:

npm install @testing-library/react @testing-library/jest-dom --save-dev

Write integration tests using Testing Library:

import { render, screen } from '@testing-library/react';
import App from './App';

test('renders learn react link', () => {
  render(<App />);
  const linkElement = screen.getByText(/learn react/i);
  expect(linkElement).toBeInTheDocument();
});

Conclusion

This section introduced you to enhancing your Next.js application's quality by adding unit and integration tests using testing libraries such as Jest or Testing Library. By performing tests, you can ensure the reliability and functionality of your application, while effectively detecting and addressing issues.