Jest vs Mocha: A Comparison of JS Testing Frameworks

May 28, 2023 11:44 · 949 words · 5 minute read javascript jest testing

Looking to choose between Jest and Mocha for your JavaScript testing needs? Dive into this detailed comparison of the two popular testing frameworks. Discover their similarities, differences, strengths, and weaknesses to make an informed decision.

Read on to find out which framework suits your testing requirements best.

According to the Stack Overflow survey of 2021, JS emerged as the most favored language among programming, scripting language and markups, a position it retained in 2022 as well.

When it comes to testing JavaScript code, an array of testing frameworks exists to facilitate thorough feature testing on a large scale. Among the available frameworks, the following are ranked based on their usage over the years. In this article, we will compare two famous testing frameworks, Jest and Mocha , to aid you in determining which one to begin with for unit testing in Node.js.

Overview: Jest vs Mocha

Introduction to Jest

Jest stands as a leading open-source testing framework — JavaScript meticulously crafted by Facebook. Its primary focus revolves around facilitating the testing endeavors of React, Angular, Node and other JavaScript-driven applications.

Esteemed for its remarkable capabilities in test automation, Jest presents itself as an all-encompassing solution. With a built-in test runner and a dedicated mocking library, there arises no necessity to install or integrate supplementary dependencies for mocking, spying, or making assertions. By leveraging the seamless installation process, test cases can be promptly scripted upon Jest’s setup, ushering in an efficient and streamlined testing experience.

Introduction to Mocha

Mocha emerges as a JavaScript testing framework meticulously tailored for the examination of applications operating within the NodeJS environment. It empowers developers with a robust foundation for conducting diverse forms of testing, ranging from Unit and Integration to End-to-End assessments and beyond.

By furnishing a fundamental test framework, Mocha lays the groundwork for comprehensive testing endeavors. Moreover, it extends its utility by offering a wide array of assertion, mocking, and spy libraries, albeit requiring separate installations. Among the favored options in this domain, Chai and Sinon enjoy widespread popularity.

Differences: Jest vs Mocha

Aspect	Jest	Mocha
Programming Language	Primarily JavaScript	Primarily JavaScript
Testing Tool Type	Test runner	Testing framework
Description (General)	Widely used framework for test development	Primarily focuses on Simplicity and support for large web applications
Testing Category	Unit testing, Integration testing, End-to-End testing	Unit testing
Supports	Rational conjunctions	Does not support rational conjunctions
Testing Functions	Uses two functions to run a test: Describe & IT	Uses only one function to run a test: Test
Snapshot Testing	Does not support	Built-in support
Asynchronous Testing	Supports for asynchronous testing	Does not support
Library Functions	Requires additional libraries to work	Requires no preconfiguration
Originally Designed for	NodeJS applications	React applications
Companies Using it	Used by numerous companies, including Accenture, Yahoo, Netifly, etc.	Widely adopted by companies such as Facebook, Airbnb, Twitter, Instagram, etc.

Performance and Speed: Jest vs Mocha

Performance is a critical aspect of any testing framework, as it directly impacts the efficiency and productivity of developers. In the JavaScript ecosystem, two popular testing frameworks, Jest and Mocha, are widely used. Let’s explore the performance benchmarks of each framework to gain insights into their speed and efficiency:

Performance Benchmarks of Jest

Jest, known for its ease of use and extensive feature set, has made significant strides in optimizing its performance over the years. Several factors contribute to Jest’s performance, including its parallel test execution capability and intelligent test file selection mechanism.

Jest's parallel test execution allows multiple tests to run concurrently, taking advantage of multi-core processors and reducing the overall testing time.

This feature is particularly beneficial for large projects with extensive test suites, as it maximizes resource utilization and minimizes idle time.

Lastly, Jest incorporates a smart test file selection mechanism. By utilizing a file dependency graph, Jest can intelligently select only the relevant test files to run, skipping unnecessary tests and improving execution speed. This selective execution strategy eliminates redundant tests and optimizes resource utilization.

Performance Benchmarks of Mocha

Mocha, known for its flexibility and modularity, offers a different approach to performance optimization. Mocha focuses on providing a lightweight core framework while allowing developers to choose and integrate additional tools and plugins to enhance performance as needed.

The performance of Mocha largely depends on the specific configuration and setup chosen by developers.

Mocha itself does not have built-in parallel test execution or test file selection mechanisms like Jest.

However, developers can leverage external libraries and tools to achieve parallelization and optimize test file selection in Mocha.

By utilizing tools like Mocha-parallel-tests or Mocha-parallel-supertest, developers can introduce parallel execution capabilities in Mocha. The Mocha testing framework, along with these libraries, excels in distributing tests across multiple processes. This intelligent allocation of resources optimizes efficiency and significantly diminishes the overall testing time.

Pros and Cons: Jest vs Mocha

Jest	Mocha
Pros Lightweight and fast Suitable for microservices Easy integration with AWS Built-in support for serverless apps Efficient development workflow Scalable and fault-tolerant Strong ecosystem and plugins	Pros Flexible and highly customizable Supports multiple testing frameworks Extensive reporting capabilities Seamless integration with Node.js Rich set of assertion functions Well-documented and active community Provides easy setup and configuration
Cons Limited support for non-Java apps May require additional libraries More complex configuration Relatively new and evolving	Cons Steeper learning curve for beginners Requires Node.js environment Limited support for certain features Requires additional learning for advanced testing mocha strategies

Final Thoughts

When it comes to testing mocha , Jest stands as a favorable choice over Mocha. Notably, Jest seamlessly integrates with BrowserStack, a comprehensive platform that extends compatibility to various automation frameworks such as Selenium, Cypress, Playwright, Puppeteer, and more.

By leveraging this powerful combination, your organization can effortlessly scale its agile initiatives. By conducting tests on genuine browsers and devices, the software development cycle is expedited, allowing for enhanced efficiency and productivity.