Jest Tutorial: Complete Guide to Jest Testing

Jest is a testing framework that allows you to write tests in an approachable, familiar, and feature-rich API. Jest provides quick test results and ensures correctness in your codebase.

Jest Testing

What is Jest?

Jest is a JavaScript-based framework for testing React, React Native and other JavaScript-based applications. In many cases, unit tests don't provide accurate results when run on the frontend of any software. Jest reduces this issue by allowing you to write faster, more effective front-end tests.

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

In addition, Jest can be used to validate almost anything around JavaScript, especially the browser rendering of web applications. With its intuitive API and easy setup and installation, Jest has become one of the most popular JavaScript testing frameworks available today.

With a built-in mockery library, an assertion library, and a test runner, Jest acts as a full-stack testing framework that allows you to write tests for JavaScript Library Projects such as AngularJS, Vue JS, Node JS, Babel, and TypeScript.

The Rise of Jest Framework

Initially created by Facebook, Jest is a popular testing framework for React applications. Since then, the tool has grown in popularity and is used for testing both front-end and back-end applications.

Facebook, Airbnb, Spotify, The New York Times, Travel Perk, Twitter, and Instagram are among the prominent companies that reportedly adopt Jest in their tech stack.

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

Satisfaction:

According to the State of JS survey, Jest has been the most interesting and satisfying framework for JavaScript testing. There has been a constant rise in the level of satisfaction among the tester community ( 59% in 2016 to 93% in 2021).

Jest Satisfaction

Interest:

The interest among the developers and testers community has also shown a consistent rise, i.e., from 59% in 2016 to 79% in 2021.

Jest Interest

Usage:

According to the State of JS survey, Jest has been the most widely used testing framework for JavaScript testing, among other frameworks. It shows a significant rise from 8% in 2016 to 73% in 2021.

Jest Usage

Awareness:

Since 2016, Jest has shown a consistent rise in its awareness among the tester community. Not only this, prominent companies like Facebook, Spotify, Airbnb, Twitter, etc, have also adopted Jest in their tech stack. It has shown a significant rise from 36% in 2016 to 95% in 2021.

Jest Awareness

The State of JS survey also shows that 57 % of testers and developers would like to use it again for their testing needs, and around 15% would like to learn Jest.

Jest Statistics

Why TestCafe?

TestCafe has several features that make it easier to use than competing solutions.

  • TestCafe is fast to download, easy to install and configure, and requires minimal setup time.
  • It can run test scripts without using or depending on external libraries like external jars, WebDriver, etc.
  • Enables developers and testers to be more productive by simplifying the process of writing tests.
  • It can run tests on all major browsers - Chrome, Edge, Safari, Firefox and IE.
  • TestCafe has built-in waiting functionality.

Features of Jest

There are many automated frameworks that are used for cross-browser testing. But Jest is better than the rest. Here's why:

  • Jest is faster than other frameworks when it comes to executing test cases. In addition to speeding up the entire test suite, Jest offers great efficiency in its watch mode enabling users to analyze how specific changes affect the overall output.
  • Jest framework offers pre-commit hooks, which are an effective method to reduce the number of tests performed by a test suite. These tests are popularly known as snapshot tests and are useful in reducing regression testing efforts.
  • Jest comes with all of the features that are required in a modern testing framework. Built-in modules provide good support for plugins, and there is no need to download any other third-party executable, like Mocha or Cucumber, to perform certain activities. In case you need to add any other library with Jest, they are easily configurable and there are no compatibility issues.
  • Migrating a current test project to the Jest framework is easy and can be done programmatically using code mods module.
  • The framework is not just a basic test runner; on the other hand, it also offers advanced features such as auto mocking modules, coverage thresholds, and mappers. This includes support for multiple projects in the same runner and customer resolvers such as Babel and Webpack.

According to the StateofJS survey, here are some other reasons why developers prefer Jest over other frameworks.

Why Use Jest

Limitations of Jest Testing

Jest's biggest weakness is that it is a newer and less widely used framework among JavaScript developers. It has less tooling and library support available compared to more mature libraries (like Mocha). This can be a big drawback for developers who want to run and debug their tests in an IDE like WebStorm.

Using auto-mocking features can slow down your test suite. This is because the more dependencies a module has, the more work Jest needs to do to fake them out and make them behave like real dependencies to test your code.

Along with this, snapshot testing with Jest is not a good fit for projects that produce large snapshot files with thousands of lines.

Jest Architecture

To get a deep understanding of how Jest works, understand its architecture, here is an official video by the creators of Jest.

Jest vs Mocha: A Detailed Comparison

To get started, Jest was designed to be used as a single, standalone testing framework that requires no external dependencies. On the other hand, Mocha is designed to work with a selection of other libraries, which means that developers need to specify which library they want to use. In addition, Mocha does not require strict requirements for setting up these libraries, making it a more optimized tool, so it can be used more easily and efficiently than other comparable tools.

Another feature worth mentioning is that Jest is considered easier to learn than other testing tools, which might be an advantage for developers who are just beginning to use the TDD approach. Additionally, although Jest does not support logical conjunctions or disjunctions, Mocha (with Chai assertion library) does. Along with this, Jest has built-in support for both Asynchronous and Snapshot testing, whereas Mocha doesn’t. Mocha framework supports Unit testing, Integration testing, and end-to-end testing under the testing category, whereas Jest only supports Unit testing.

Jest vs Mocha

The graph above presents data from npm trends, showing that Jest has a much stronger position than Mocha, and almost doubles Mocha's weekly downloads. On the other hand, Mocha is presented as a more stable and compact solution with fewer issues than Jest.

Browsers Supported by Jest

Jest is compatible with all major browsers, including:

  • Google Chrome (27 & above)
  • Firefox (10 & above)
  • IE (9 & above)
  • Opera (69 & above)
  • Safari (7.1 & 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.
  • Live interactive cross browser testing in different environments.
  • Perform Mobile App testing on Real Device cloud.
  • Perform 70% faster test execution with HyperExecute.
  • Mitigate test flakiness, shorten job times and get faster feedback on code changes with TAS (Test At Scale).
  • Smart Visual Regression Testing on cloud.
  • LT Browser - for responsive testing across 50+ pre-installed mobile, tablets, desktop, and laptop viewports.
  • Capture full page automated screenshot across multiple browsers in a single click.
  • Test your locally hosted web and mobile apps with LambdaTest tunnel.
  • Test for online Accessibility testing.
  • 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 Jest Tests on LambdaTest?

Jest cloud grids like LambdaTest allow you to perform Jest 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 Jest automation testing script online, refer to our GitHub repository. No need to worry about the challenges with Jest infrastructure. Want to know a fun fact? Your first 100 Jest 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 Jest Grid.

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

Frequently Asked Questions

What is Jest?
Jest is a JavaScript-based testing framework that enables you to write tests for your code quickly. Jest was designed and built on top of Jasmine by Christoph Nakazawa and maintained by Meta. with a focus on simplicity, performance, and support for large applications.
What is the difference between Jest and Selenium?
Jest is a popular Javascript-based testing framework, while Selenium is commonly used for browser testing. Many developers prefer Jest, because it's open source, whereas Selenium is popular primarily because it automates browsers.
What is Jest used for?
Jest is a JavaScript library that simplifies the process of testing React applications, making it easier to write tests and improve code quality.
Is Jest a unit testing framework?
Jest framework allows you to write clean unit tests like other xUnit based unit test frameworks, by providing hooks for setup and cleanup methods.
What are the benefits of Jest for automation?
Jest is JavaScript based test automation framework with in-built support for Jasmine and Selenium. It's easy to setup and get started with, comes with great community support, and comes with easy CLI support.
Can I run Jest scripts on LambdaTest?
The LambdaTest Selenium Automation Grid allows you to run Jest automation tests on a secure, robust, and scalable JavaScript test execution cloud. With LambdaTest you can run your JavaScript Selenium tests at scale across 3000+ different environments in parallel, resulting in higher test coverage and much shorter build times. Refer to our Jest documentation to know more.
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