Writing Tests in Express.js Projects: Using Jest and Supertest

Developing web applications is not just about writing code. Writing tests to verify that your code runs correctly and produces the expected results is also extremely important. In this article, you will learn how to use the Jest and Supertest libraries to write tests in Express.js projects. Writing tests increases the maintainability of projects and makes the debugging process easier.

The Importance of Writing Tests

There are many advantages to writing tests. First of all, it allows you to detect errors that may arise during the application development process early on. In this way, you ensure the functionality of the integrated features in the project. Also, it reduces costs in the long term since it gives you the opportunity to check whether existing functions are broken or not when making changes to the code or adding new features.

Writing Tests with Jest and Supertest

Jest is a popular testing framework for JavaScript projects and has a user-friendly interface. Supertest is a library used for sending HTTP requests and is ideal for Express.js applications. With the following steps, you will see how you can write tests with Jest and Supertest in your Express.js application.

Installation

npm install --save-dev jest supertest

Creating a Simple Express.js Application

const express = require('express');
const app = express();

app.get('/api/greeting', (req, res) => {
    res.status(200).send({ message: 'Hello, World!' });
});

module.exports = app;

Creating the Test File

const request = require('supertest');
const app = require('./app');

test('GET /api/greeting', async () => {
    const response = await request(app).get('/api/greeting');
    expect(response.statusCode).toBe(200);
    expect(response.body.message).toBe('Hello, World!');
});

Conclusion

Writing tests in Express.js projects using Jest and Supertest is an effective way to increase the reliability of your application. Writing these tests not only provides assurance that the application will not behave unexpectedly but also improves your developer experience. If you make writing tests a part of your project, you will have a more sustainable and reliable code base in the long term.