Mocha Test Tutorial: Complete Guide to Mocha Testing

Mocha is a feature-rich JavaScript-based testing framework that simplifies asynchronous testing. Run tests serially, enabling flexible and accurate reporting, while at the same time mapping uncaught exceptions to the correct test cases.

Mocha.js Testing

What is Mocha.js?

The Mocha testing framework provided as a NodeJs module and a browser script makes asynchronous testing simple and fun. In addition, the framework's ability to run tests serially allows tests to be flexible and accurate without sacrificing speed or accuracy.

Note: You can also run your Mocha.js test scripts on LambdaTest cloud.

Mocha provides a way to write a structured code for testing the applications thoroughly, classifying them into test suites and test cases. Mapping errors to corresponding test cases allows us to produce a test report after the run.

Mocha supports any number of test interfaces, including TSS, Exports, QUnit, and Require. The default interface is a behavior-driven development (BDD), which aims to help developers build software that is predictable, resilient to changes, and not error-prone.

The Rise of Mocha.js Framework

According to StackOverflow insights 2021, JavaScript is the most popular programming language. As web and mobile power grows daily, JavaScript and JavaScript frameworks are becoming increasingly important.

JavaScript frameworks have emerged that allow testers to create complete end-to-end automation test suites, not just unit test cases. Mocha is a JavaScript testing framework that has been particularly popular since 2016, as per StateofJS 2021.

Check out The State of JS 2021 Mocha.js testing data on the basis of developer Satisfaction, Interest, Usage and Awareness.


Since 2016, Mocha has shown a constant decrease in the percentage of satisfying the testers and developer community. The level of satisfaction has dropped from 94% in 2016 to 69% in 2021.

Mocha.js Satisfaction


The percentage of interest shown by the tester and developer community for using Mocha has also shown a significant drop over the last 5 years. The percentage has dropped from 75% in 2016 to 45% in 2021.

Mocha.js Interest


The change in the level of usage of Mocha among testers hasn’t shown a significant change since its inception. The percentage varies from 49% in 2016 to 50% in 2021.

Mocha.js Usage


The percentage of awareness about Mocha among the tester community has seen a slight increase, indicating growth potential i.e., from 89% in 2016 to 90% in 2021.

Mocha.js Awareness

As per the experience over time section, the overall interest among the tester community to use Mocha has seen a constant downfall in the last 5 years. There is also a decrease in the percentage of testers who would like to use Mocha again, from 45.6% in 2016 to 34.6% in 2021.

Mocha.js Statistics

Why Use Mocha.js Framework?

  • A number of installation options: It can be installed globally, as a development dependency for your project, or set up to run test cases directly on the web browser.
  • Multiple browser support: Mocha makes it easy to create test cases that run seamlessly on all major web browsers. It can be extended with plugins, and each revision of Mocha provides upgraded JavaScript and CSS build for different web browsers.
  • Various ways to offer test reports: It provides users with a variety of reporting options, such as the list reporter, the progress reporter and the JSON reporter, which allows you to choose the one that best suits your needs.
  • Supports JS assertion libraries: With Mocha, you can reduce testing costs and speed up the process by having compatibility for various JavaScript assertion libraries—Express.js, Should.js, Chai. This multiple library support makes it easier for you to write lengthy and complex test cases, so if everything works fine, you won't have to rewrite them again.
  • Supports both BDD and TDD environments: Mocha supports both behavior-driven development (BDD) and test-driven development (TDD), making it easy to write high-quality tests and enhance coverage.
  • Supports both synchronous and asynchronous testing: Mocha is designed to fortify asynchronous testing with features that invoke the callback once the test is finished. It enables synchronous testing by omitting the callback.

Limitations of Mocha.js Testing

  • Compared to other frameworks, Mocha requires more configuration, making it less flexible.
  • In the case of Mocha, if you are unable to afford flexibility, then you must choose an assertion library explicitly.
  • Mocha snapshot testing can be tricky. To do it well, you'll need to work with the chai-jest-snapshot library.

Mocha.js vs Jasmine: A Detailed Comparison

Jasmine is a JavaScript testing framework that was created around 2008 and has been updated regularly since. The documentation describes it as “batteries included,” meaning that it attempts to provide everything a developer needs in a testing framework. Whereas, Mocha, created in 2011, is a younger framework than Jasmine. It is not a “complete” framework; instead, it covers the basics and allows developers to extend it with other frameworks.


Assertions are Boolean functions that test behavior. A true result from an assertion indicates that the expected behavior occurred when the test ran. Jasmine includes a library of assertions that use an expect-style syntax. While Mocha does not have a built-in assertion library, developers can use the popular Chai assertion library, which uses a syntax similar to Jasmine.

Test Doubles/Spies:

Test double frameworks, such as Jasmine, create test doubles. A test double, or spy, is like a clone of an object. It has the same functions as the original object. However, those functions are "stubbed out," meaning they don't do anything. The "stubbed" functions exist so the test double framework can "watch" the double in action, tracking calls to its functions. Mocha does not include a spy framework, but SinonJS is a popular choice for creating spies.

In conclusion, Jasmine comes with assertions and spies, but it doesn’t necessarily make it a better option than Mocha. Mocha focuses on BDD test definitions and does so very well, but other best-of-breed frameworks combine with Mocha to extend its functionality.

To make an informed choice, try both Mocha and Jasmine. Your particular application, and the needs of the test suite will make one option clear as you experiment. You can use either library on its own, but to keep your tests consistent and readable, we recommend combining Mocha or Jasmine with Chai and Sinon within an application.

Browsers Supported by Mocha.js

Mocha.js is compatible with all major browsers, including:

  • Google Chrome (27 & above)
  • Firefox (10 & above)
  • IE (10 & above)
  • Opera (69 & above)
  • Safari (7.1 & above)
  • Edge (15 & above)

About LambdaTest

LambdaTest is a leading test execution and orchestration platform that is fast, reliable, scalable, and secure. It allows users to run both manual and automated testing of web and mobile apps across 3000+ different browsers, operating systems, and real device combinations. Using LambdaTest, businesses can ensure quicker developer feedback and hence achieve faster go to market. Over 500 enterprises and 1 Million + users across 130+ countries rely on LambdaTest for their testing needs.

What does LambdaTest offer?

  • Run Selenium, Cypress, Puppeteer, Playwright, and Appium automation tests across 3000+ real desktop and mobile environments.
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  • Mitigate test flakiness, shorten job times and get faster feedback on code changes with TAS (Test At Scale).
  • Smart Visual Regression Testing on cloud.
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  • Test your locally hosted web and mobile apps with LambdaTest tunnel.
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  • Test across multiple geographies with Geolocation testing feature.
  • 120+ third-party integrations with your favorite tool for CI/CD, Project Management, Codeless Automation, and more.

How To Run Mocha.js Tests on LambdaTest?

Mocha.js cloud grids like LambdaTest allow you to perform Mocha.js testing at scale. LambdaTest allows you to perform automated cross browser testing on an online browser farm of 40+ browsers and operating systems to expedite the test execution in a scalable way. Moreover, it increases the test coverage with better product quality.

To run your first Mocha.js automation testing script online, refer to our GitHub repository. No need to worry about the challenges with Mocha.js infrastructure. Want to know a fun fact? Your first 100 Mocha.js automation testing minutes are on us with just a free sign-up. You can also avail benefits of manual cross-browser testing, responsive testing, and more with a lifetime of free access to LambdaTest, the world's fastest-growing cloud Mocha.js Grid.

Our detailed Mocha.js tutorials will help you develop a better functional understanding of the Mocha.js framework. Finally, kick-start your Mocha.js automation journey by running your first Mocha.js test script on the LambdaTest cloud.

Learning Resources for Mocha.js

Run your first Mocha.js test with our detailed video tutorials:

Frequently Asked Questions

What is Mocha testing?
Mocha is a JavaScript-based test framework for Node.js and the browser, making asynchronous testing simple and fun. It allows for flexible and accurate reporting and maps uncaught exceptions to the correct test cases.
Is Mocha used for unit testing?
Mocha is a Node.js testing library designed to be a simple, extensible testing solution for both unit and integration testing. Thousands of developers use it, and it's a great candidate for BDD (Behavior Driven Development).
Which is better Jest or Mocha?
Jest is a faster testing tool than Mocha, as it has built-in support for snapshot testing. Snapshot testing makes it easy to keep tests up to date as you work, so you don't have to worry about getting off track. On the other hand, since Jest is newer and the community is smaller, Mocha has more out-of-the-box features.
What is automated testing with Mocha?
Mocha is an open-source JavaScript-based test framework that helps you write better-quality code by running your automated tests in Node. It offers out-of-the-box features such as creating descriptive automated tests, robust reports, and even executing your tests whenever any files are changed locally.
What is difference between Mocha.js and Selenium?
Selenium is an open-source test automation framework for testing websites and webapps. Used mainly for end-to-end automation of browser based web testing, it is the most popular automation testing framwork. Mocha.js on the other hand, picks up where selenium gets left off. It extends selenium and is a full featured test automation framework that can used for everything including unit tests, end-to-end tests, integration tests, and much more. In most practical use cases developers and testers do not use just vanilla Selenium. Users usually use both Selenium and frameworks like Mocha.js together.
How can I automate with Mocha.js using LambdaTest?
LambdaTest online Selenium Automation Grid enables you to run end-to-end Mocha.js tests on a secure, robust, and scalable Selenium grid infrastructure. With LambdaTest, you can run Python based tests across 3000+ different browsers in parallel. You get higher test coverage and at the same time much shorter build times. Refer to our Mocha.js documentation.

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