Comparing the best Node.js unit testing frameworks

Editor’s note: This comparison of Node.js unit testing frameworks was last updated on 27 May 2022 to include the most recent survey data and remove outdated information.

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.

Here’s what we’ll cover:

• What are the benefits of unit testing in Node.js?
• What makes a good Node.js testing framework?
• What are the best Node.js unit testing frameworks?
• Mocha
• Jest
• Jasmine
• Ava
• Choosing the best unit testing framework for your project

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.

Let’s look at some 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.

Third, the debugging process is made a lot easier. This is because when the test fails, the focus will be on the latest changes made.

Fourth, refactoring code is made easier, because changes can be verified using tests to ensure that the unit being tested still behaves in the desired manner.

Finally, costs that would be incurred 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.

What makes a good Node.js testing framework?

There are a thousand and one testing 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 2021,” the most popular JavaScript testing frameworks and libraries in 2021 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 four of these Node.js unit testing frameworks:

• Mocha
• Jest
• Jasmine
• AVA

Mocha

Mocha has been around for quite a while; it was initially released in November 2011. However, unlike other frameworks like Jest and Jasmine, it relies on third-party assertions, mocking, and spying tools like Sinon and Chai. It 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 plan 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 loads of 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 on how to use it
• 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.

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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 a lot of 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);
});

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.

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.