Comparing the best Node.js unit testing frameworks

Editor’s note: This comparison of Node.js unit testing frameworks was last updated on 3 July 2023 to include the most recent survey data, and other popular testing frameworks, such as Supertest and Webdriver.

In this Node.js unit testing guide, I’ll provide some reasons why you should unit test your Node apps, discuss what makes a good testing framework, and compare some of the most popular Node unit testing frameworks available today.

What are the benefits of unit testing in Node.js?

Unit testing is a software testing method in which individual pieces of code (usually the smallest piece of code that can be logically isolated in a system) are tested in isolation. Unit tests should be isolated so that there are no external dependencies.

There are many advantages associated with unit testing. First, unit testing makes it easier to identify bugs in code. Appropriate test cases should be written for every piece of code to ensure that they meet specifications and provide the desired output. Any changes that result in failing tests will indicate that an error or bug has been introduced. Additionally, unit testing makes it easier to narrow down the offending piece of code.

Second, unit tests act as self-documentation. A new team member can gain a better understanding of the codebase by going through unit tests. Additionally, the debugging process is made a lot easier with unit tests. This is because when the test fails, the focus will be on the latest changes made.

Refactoring code is also made easier with unit testing because changes can be verified using tests to ensure that the unit being tested still behaves in the desired manner. Unit testing also reduces the costs that can be incurred by fixing bugs or system outages are reduced.

Testing frameworks provide a set of reusable components or modules, such as test runners and utilities, for running automated tests. The testing framework is responsible for:

1. Describing the format used to convey test expectations
2. Creating a way of accessing the application or code to be tested
3. Executing the tests
4. Reporting test results

They are particularly useful when tests are an integral part of your continuous integration process. Frameworks are built for a specific type of testing: unit, integration, functional, or combinations of these.

Criteria for a good Node.js testing framework

There are countless frameworks out there. To pick something that works for your use case, you need to evaluate each framework based on your project needs and how effective you consider it to be for your team. Below are six key characteristics of a strong Node.js testing framework:

1. Ease of setup: Getting up and running with your tests should take a minimal amount of effort
2. Well-supported: There is plenty of excellent documentation and communities to get help
3. Wide array of feature sets: The framework has things such as matchers, spies, and mocking built in
4. Speed: For tests that are CPU-bound, choosing the right framework can save you a lot of time during test runs
5. Ease of reporting: Coverage reports should be easy to generate using built-in reporting and external reporting libraries should be easy to integrate
6. Ease of integration: A good testing library should be easy to integrate into your continuous integration process

What are the best Node.js unit testing frameworks?

According to The State of JavaScript 2022, the most popular JavaScript testing frameworks and libraries in 2022 were Testing Library, Vitest, Jest, Cypress, Playwright, and Storybook. Rounding out the top ten are Puppeteer, Mocha, Jasmine, AVA, and WebdriverIO:

In this guide, we’ll compare eight of these Node.js unit testing frameworks:

• Mocha
• Jest
• Jasmine
• AVA
• Chai
• Sinon
• Supertest
• Webdriver

Mocha

Mocha has been around for a while; it was initially released in November 2011. However, unlike other frameworks like Jest and Jasmine, Mocha relies on third-party assertions, mocking, and spying tools like Sinon and Chai. This framework is very extensible and has a lot of plugins, extensions, and libraries designed to run on top of it.

Pros:

• Highly extensible with support for various assertion and mocking libraries
• Easy asynchronous testing
• Adding support for generators to test suites is relatively easy. Using the co-mocha package, all you have to do is require it in your tests and you’re ready to use generators
• Supported by some CI servers and plugins for others

Cons:

• The use of extra libraries can introduce configuration complexity and increases maintenance work
• No auto-mocking

Sample Mocha test:

const { expect } = require('chai');
    describe('Sum numbers', () => {
      it('should add two numbers correctly', () => {
        const sum = 1 + 2;
        const expectedResult = 3;
        expect(sum).to.equal(expectedResult);
      });
    });

Jest

Jest is a JavaScript testing framework developed and regularly maintained by Facebook. Its popularity has grown steadily since 2016, when only six percent of respondents to that year’s State of JS survey said they had used Jest before and would use it again. This figure climbed to a quarter of respondents in 2017 before reaching 40 percent in 2018. As of the most recent edition, a whopping 73 percent of JavaScript developers had tried Jest and planned to use it again.

Pros:

• Comprehensive documentation includes detailed instructions to help you set up testing, write various types of tests, and use its many features, as well as great examples
• Easy setup with flexible and easy configuration and less boilerplate code than other frameworks
• Parallel test running enabled
• Optimal performance: tests are parallelized by running them in their own processes to maximize performance
• Useful features such as snapshots, coverage, and test watching

Cons:

• Displays multiple messages for the same error
• It can require more dependencies during initial setup (e.g., Babel)

Sample Jest test:

describe("Sum numbers", () => {
  test("it should sum two numbers correctly", () => {
    const sum = 1 + 2;
    const expectedResult = 3;
    expect(sum).toEqual(expectedResult);
  })
});

Jasmine

Developed by Pivotal Labs and released in 2010, Jasmine has been around for a lot longer than Jest. It aims to run on any JavaScript-enabled platform and is highly flexible and compatible with a variety of other testing frameworks and libraries, including Sinon and Chai. Due to its longevity, it has developed a significant community and enjoys ample support with many libraries, blog articles, and tutorials.

Pros:

• Simple to set up — Jasmine has a CLI tool that creates a spec folder and a JSON configuration file, so with one command you’re ready to start testing your code
• Thoroughly tested, documented, and supported by numerous tutorials
• Behavior-driven development focused with descriptive syntax
• Supported by many CI servers with plugins available for those that don’t have out-of-the box support

Cons:

• Unfriendly error logs
• Test files must have a specific suffix (e.g., spec.js)
• Assertion library is not as rich as Chai

Sample Jasmine test:

describe("Sum numbers", function() {
  it("should sum two numbers correctly", function() {
    var sum = 1 + 2;
    var expectedResult = 3;
    expect(sum).toEqual(expectedResult);
  });
});

AVA

Minimalism is the focus of AVA. It has a simple API while still supporting advanced features. It achieves its blazing speed by running tests in parallel as separate Node processes. Unlike other testing frameworks such as Jest and Jasmine, it does not create test globals.

Pros:

• Easy to use. To install and setup AVA, all you have to do is run npm init ava
• Parallel test running
• Native ES6/ES7 support
• Built-in support for async functions
• If a promise is returned, you don’t need to end the test yourself; it will end when the promise resolves

Cons:

• AVA is relatively new. The community is still growing and there isn’t a lot of documentation or tutorials like other testing frameworks
• AVA has many open issues on GitHub

Sample Ava test:

import test from 'ava';
test('Sum numbers', t => {
  const sum = 1 + 2;
  const expectedResult = 3;
  t.equal(sum, expectedResult);
});

Chai

Chai is an assertion library that follows a test-driven or behavior-driven development. You can easily pair it with any JavaScript testing framework such as Mocha for your application. Chai provides one of the best surface-level APIs and allows you to choose the interface that you are most comfortable with.

Pros:

• Provides a very expressive and readable syntax for writing assertions
• Allows you to choose your own style for writing assertions such as expect, should, assert
• Integration is one of the major benefits of using Chai. You can customize it to use along with Mocha, Jasmine, etc.
• It is actively maintained and has a rich developer ecosystem

Cons:

• Chai lacks strong TypeScript support. While you can extensively use it in a TypeScript codebase, you might need to rely on additional typings and configurations
• Too many assertion tests might cause performance overhead if used incorrectly
• There is a possibility of overusing assertion tests due to the multitude of tests provided by Chai

Sample Chai test:

// import chai
const { expect } = require('chai'); 

// write your function
function add(a, b) { 
return a + b; 
} 

// write assertions, you can also use `expect` or `should` interfaces
describe('add', () => {
it('should return the sum of two numbers', () => {
const result = add(10, 20);
expect(result).to.equal(30); 
});

Sinon

Sinon is another powerful JavaScript library that is used to create tests for your applications. It provides key features such as stubs, spies, mocks, fake timers, etc. that are helpful when writing tests for isolated functions and logic. Sinon also integrates well with existing assertion libraries such as Chai and Jasmine. These assertions help by making code more robust based on the concept of stubs, spies, mocks, etc.

Pros:

• Sinon concepts help you with controlling how a function behaves by isolating its dependencies, interactions, etc.
• Sinon has a very flexible syntax and is expressive
• It offers a concept of time manipulation, where you can control and manipulate time-dependent functions and code by using fake timers

Cons:

• Has a steep learning curve. You have to learn its various concept, such as stubs, fake timers, and spies, which are not common with other assertion libraries
• The concept of stubs and fake timers has a performance overhead; you might run into issues if you’re not careful
• You need to be extremel;y careful about the dependency management with Sinon. As you include Sinon in your application, you have to make sure all the libraries and external dependencies are compatible with each other

Sample Sinon test:

const sinon = require('sinon'); 
const { expect } = require('chai');

// a simple async function that fetches data from a remote server
function fetchData(url) {
 return fetch(url)
  .then(response => response.json())
  .catch(error => {
      console.log('API Error:', error);
   throw error;
  });
}

describe('fetchData', () => {
 let fetchStub;

// beforeEach comes from your testing framework like Mocha/Jasmine
 beforeEach(() => {
  // creating a stub for async fetch function
  fetchStub = sinon.stub().resolves({
   json: () => ({ data: ‘Data’ })
  });
 });

// afterEach comes from your testing framework like Mocha/Jasmine
 afterEach(() => {
  // restoring
  fetchStub.restore();
 });

// write test cases
it('should fetch async data', async () => {

  // pass a url for async requests to get data
  const url = 'https://jsonplaceholder.typicode.com/todos';

  // replace fetch function with `fetchStub`
  sinon.replace(window, 'fetch', fetchStub);

  // verify the data if it matches   
  const result = await fetchData(url);

  expect(result).to.deep.equal({ data: ‘Data' }); 
 });
}

Supertest

Supertest is another library that is used for testing HTTP servers and making assertions against the response. It provides high-level API for sending HTTP requests and making assertions, this would help you with testing out server-side code.

Pros:

• Easy to use and provides a very intuitive API
• Lightweight and takes little resources to make assertions against the response
• Has built-in support for async requests, making it the best in the ecosystem to test your server response code
• It is also flexible enough to customize the HTTP request, including its headers, query params, form data, etc.

Cons:

• Similar to a few libraries out there, Supertest also lacks proper TypeScript support and you have to rely on additional type safety or configurations
• Built around the Express.js ecosystem, while you can surely integrate it with other server libraries out there, it requires effort
• The documentation is non-existent. There is one README file that is hosted on GitHub, but that is it. For complex scenarios, you need to dig up its source code itself
• This library is great, but it lacks an ecosystem. You won’t be able to find many production codebase examples out there

Sample Supertest test:

const request = require('supertest');
const assert = require('assert');
const express = require('express');

const app = express();

app.get(‘/posts, function(req, res) {
 res.status(200).json({ name: ‘first_post });
});

request(app)
 .get(‘/posts’)
 .expect('Content-Type', /json/)
 .expect(200)
.end((error, result) => {
  if(error){
    throw error
  }
})

Webdriver

Webdriver is an open source library that provides a collection of APIs for browser automation testing. These APIs allow you to control and interact with the browser programmatically. WebDriver supports a range of languages including Python, JavaScript, etc. It provides APIs powerful enough to work on different sets of browsers and frameworks.

Pros:

• Supports multiple browsers and allows you to write automation scripts for a range of frameworks
• Allows you to write very complex browser interactions including drag and drop, clicks, keyboard inputs, etc.
• Has a very extensive documentation and good community support
• Can integrate with existing test runners, assertion libraries, etc.

Cons:

• Working with Webdriver might backfire as it creates a lot of time doing web automation programmatically. It might have execution issues
• Relies heavily on browser-specific drivers. You have to ensure all configs are in place for that to happen correctly for the target browser
• It is somewhat limited to non-browser automation tasks. You might need to pair it with other testing libraries to test out different sets of features

Sample Webdriver test:

import { remote } from 'webdriverio'

// initialize browser for automation & test
const browserContainer = await remote({
    capabilities: {
        browserName: 'chrome',
        'goog:chromeOptions': {
            // disbale hardware accelaration
            args: process.env.CI ? ['headless', 'disable-gpu'] : []
        }
    }
})

await browserContainer.url('https://google.com’)

const link = await browserContainer.$('=API')
await link.click()
// saves screenshot called "image"
await browserContainer.saveScreenshot(‘./image.png')

Choosing the best unit testing framework for your project

The table below shows a comparison of the features across four Node unit testing frameworks: Mocha, Jest, Jasmine, and AVA:

Framework	Jasmine	Ava	Jest	Mocha	Chai	Sinon	Supertest	Webdriver
Open source	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Built-in coverage reporting	No	No	Yes	No	No	No	No	No
Parallel test running	No	Yes	Yes	No	No	No	No	No
Snapshots	No	Yes	Yes	No	No	No	No	No
Built-in spies	Yes	No	Yes	No	No	Yes	No	No
Built-in mocking	Yes	No	Yes	No	No	Yes	No	No
Built-in assertions	Yes	Yes	Yes	No	Yes	No	No	No
ES2017 support	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes

The best framework can vary based on your needs, project size, and other factors. What works now might not work in the future. It’s important to take both your current and future needs into consideration when choosing the right framework.

If you want to hit the ground running, you can’t go wrong with Jest. It’s an extremely fast framework, easy to set up, and has a lot of built-in features. If you’re looking for simplicity, AVA is your best bet. It’s minimal and streamlined but capable of handling various types of Node unit tests. It is also fairly fast.

Mocha is the best choice for someone who wants flexible configurations, as well as a choice of libraries to use together with it.

There are many Node unit testing frameworks and libraries available. In this guide, we focused on four of the most popular. Remember, the best choice for you will depend on your project’s unique goals and requirements.