Jest vs Karma

Overview

Jest

Stacks15.2K

Followers4.1K

Votes175

Karma

Stacks4.8K

Followers603

Votes181

GitHub Stars12.0K

Forks1.7K

Jest vs Karma: What are the differences?

Jest and Karma are popular JavaScript testing frameworks that enable developers to write and execute tests. Let's explore the key differences between Jest and Karma in more detail:

Design Philosophy: Jest, developed by Facebook, prioritizes a seamless and intuitive testing experience for JavaScript applications. It offers built-in features like test runners, assertions, code coverage, and mocking. Karma acts as a middleware test runner, focusing on cross-browser testing and providing a flexible platform for running tests in different environments.
Features: Jest provides a comprehensive feature set including a built-in test runner, mocking, snapshot testing, code coverage reporting, and a powerful assertion library. It supports parallel test execution for faster results. Karma integrates with testing frameworks like Jasmine, Mocha, and QUnit, offering browser automation, live reloading, test result reporting, and compatibility with diverse browsers and devices.
Ecosystem Integration: Jest tightly integrates with the React ecosystem, offering additional features tailored for testing React applications such as snapshot testing. It supports frameworks like Enzyme and React Testing Library, making it popular among React developers. Karma is framework-agnostic, compatible with various JavaScript frameworks and libraries, and commonly used with Angular, Vue.js, and plain JavaScript projects.
Configuration and Setup: Jest aims to provide a zero-configuration experience by offering sensible defaults that work out-of-the-box for most projects. It requires minimal setup and can be easily integrated into JavaScript projects. Karma, on the other hand, requires more configuration and setup as it acts as a middleware between testing frameworks and browsers. It needs additional configuration files to specify the testing framework, browsers, preprocessors, and other settings.
Browser Compatibility: Jest runs tests in a Node.js environment and does not require an actual browser to execute tests. It uses jsdom, a JavaScript implementation of the DOM, to simulate the browser environment. Karma, on the other hand, allows running tests in actual browsers, enabling cross-browser testing and ensuring compatibility across different browser environments.
Community and Support: Both Jest and Karma have active and vibrant communities, with extensive documentation and support resources available. Jest, being developed by Facebook, has a large user base and benefits from the contributions and support of the React community. Karma, being a popular test runner, also has a strong community and is widely adopted across various JavaScript frameworks.

In summary, Jest and Karma are JavaScript testing frameworks with distinct design philosophies and features. Jest offers a comprehensive and intuitive testing experience with built-in features, focusing on seamless integration with the React ecosystem. Karma, on the other hand, acts as a test runner that enables cross-browser testing and works well with a variety of JavaScript frameworks.

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Advice on Jest, Karma

Dane

Feb 7, 2020

Needs adviceon

Cypress

Jest

As we all know testing is an important part of any application. To assist with our testing we are going to use both Cypress and Jest. We feel these tools complement each other and will help us get good coverage of our code. We will use Cypress for our end to end testing as we've found it quite user friendly. Jest will be used for our unit tests because we've seen how many larger companies use it with great success.

836k views836k

Comments

Anonymous

Feb 6, 2020

Needs advice

Postman will be used to do integration testing with the backend API we create. It offers a clean interface to create many requests, and you can even organize these requests into collections. It helps to test the backend API first to make sure it's working before using it in the front-end. Jest can also be used for testing and is already embedded into React. Not only does it offer unit testing support in javascript, it can also do snapshot testing for the front-end to make sure components are rendering correctly. Enzyme is complementary to Jest and offers more functions such as shallow rendering. UnitTest will be used for Python testing as it is simple, has a lot of functionality and already built in with python. Sentry will be used for keeping track of errors as it is also easily integratable with Heroku because they offer it as an add-on. LogDNA will be used for tracking logs which are not errors and is also a Heroku add-on. Its good to have a separate service to record logs, monitor, track and even fix errors in real-time so our application can run more smoothly.

290k views290k

Comments

Detailed Comparison

Jest	Karma
Jest provides you with multiple layers on top of Jasmine.	Karma is not a testing framework, nor an assertion library. Karma just launches a HTTP server, and generates the test runner HTML file you probably already know from your favourite testing framework. So for testing purposes you can use pretty much anything you like.
Familiar Approach: Built on top of the Jasmine test framework, using familiar expect(value).toBe(other) assertions;Mock by Default: Automatically mocks CommonJS modules returned by require(), making most existing code testable;Short Feedback Loop: DOM APIs are mocked and tests run in parallel via a small node.js command line utility	Test on Real Devices;Remote Control;Testing Framework Agnostic;Open Source;Easy Debugging;Continuous Integration
Statistics
GitHub Stars -	GitHub Stars 12.0K
GitHub Forks -	GitHub Forks 1.7K
Stacks 15.2K	Stacks 4.8K
Followers 4.1K	Followers 603
Votes 175	Votes 181
Pros & Cons
Pros 36 Open source 32 Mock by default makes testing much simpler 23 Testing React Native Apps 20 Parallel test running 16 Fast Cons 4 Documentation 4 Ambiguous configuration 3 Difficult 2 Many bugs still not fixed months/years after reporting 2 Difficult to run single test/describe/file	Pros 61 Test Runner 35 Open source 27 Continuous Integration 22 Great for running tests 18 Test on Real Devices Cons 1 Slow, because tests are run in a real browser 1 Requires the use of hacks to find tests dynamically
Integrations
No integrations available	Jasmine Mocha

What are some alternatives to Jest, Karma?

BrowserStack

BrowserStack is the leading test platform built for developers & QAs to expand test coverage, scale & optimize testing with cross-browser, real device cloud, accessibility, visual testing, test management, and test observability.

Selenium

Selenium automates browsers. That's it! What you do with that power is entirely up to you. Primarily, it is for automating web applications for testing purposes, but is certainly not limited to just that. Boring web-based administration tasks can (and should!) also be automated as well.

Sauce Labs

Cloud-based automated testing platform enables developers and QEs to perform functional, JavaScript unit, and manual tests with Selenium or Appium on web and mobile apps. Videos and screenshots for easy debugging. Secure and CI-ready.

Mocha

Mocha is a feature-rich JavaScript test framework running on node.js and the browser, making asynchronous testing simple and fun. Mocha tests run serially, allowing for flexible and accurate reporting, while mapping uncaught exceptions to the correct test cases.

LambdaTest

LambdaTest platform provides secure, scalable and insightful test orchestration for website, and mobile app testing. Customers at different points in their DevOps lifecycle can leverage Automation and/or Manual testing on LambdaTest.

Jasmine

Jasmine is a Behavior Driven Development testing framework for JavaScript. It does not rely on browsers, DOM, or any JavaScript framework. Thus it's suited for websites, Node.js projects, or anywhere that JavaScript can run.

Cypress

Cypress is a front end automated testing application created for the modern web. Cypress is built on a new architecture and runs in the same run-loop as the application being tested. As a result Cypress provides better, faster, and more reliable testing for anything that runs in a browser. Cypress works on any front-end framework or website.

Playwright

It is a Node library to automate the Chromium, WebKit and Firefox browsers with a single API. It enables cross-browser web automation that is ever-green, capable, reliable and fast.

Rainforest QA

Rainforest gives you the reliability of a QA team and the speed of automation, without the hassle of managing a team or the pain of writing automated tests.

CodeceptJS

It is a modern end to end testing framework with a special BDD-style syntax. The test is written as a linear scenario of user's action on a site. Each test is described inside a Scenario function with I object passed into it.

Related Comparisons

Design Philosophy: Jest, developed by Facebook, prioritizes a seamless and intuitive testing experience for JavaScript applications. It offers built-in features like test runners, assertions, code coverage, and mocking. Karma acts as a middleware test runner, focusing on cross-browser testing and providing a flexible platform for running tests in different environments.
Features: Jest provides a comprehensive feature set including a built-in test runner, mocking, snapshot testing, code coverage reporting, and a powerful assertion library. It supports parallel test execution for faster results. Karma integrates with testing frameworks like Jasmine, Mocha, and QUnit, offering browser automation, live reloading, test result reporting, and compatibility with diverse browsers and devices.
Ecosystem Integration: Jest tightly integrates with the React ecosystem, offering additional features tailored for testing React applications such as snapshot testing. It supports frameworks like Enzyme and React Testing Library, making it popular among React developers. Karma is framework-agnostic, compatible with various JavaScript frameworks and libraries, and commonly used with Angular, Vue.js, and plain JavaScript projects.
Configuration and Setup: Jest aims to provide a zero-configuration experience by offering sensible defaults that work out-of-the-box for most projects. It requires minimal setup and can be easily integrated into JavaScript projects. Karma, on the other hand, requires more configuration and setup as it acts as a middleware between testing frameworks and browsers. It needs additional configuration files to specify the testing framework, browsers, preprocessors, and other settings.
Browser Compatibility: Jest runs tests in a Node.js environment and does not require an actual browser to execute tests. It uses jsdom, a JavaScript implementation of the DOM, to simulate the browser environment. Karma, on the other hand, allows running tests in actual browsers, enabling cross-browser testing and ensuring compatibility across different browser environments.
Community and Support: Both Jest and Karma have active and vibrant communities, with extensive documentation and support resources available. Jest, being developed by Facebook, has a large user base and benefits from the contributions and support of the React community. Karma, being a popular test runner, also has a strong community and is widely adopted across various JavaScript frameworks.

Jest vs Karma