Five Essential Features of Jest for Efficient and Effective Testing

One of the most well-known tools for testing JavaScript is called Jest, created by Meta. As it works with Babel, Node, TypeScript, Angular, React, and Vue-based apps, over 3,898,000 public repositories on GitHub use it. According to Jest’s main website, it passed the 50 million download mark in July 2022. Its initial use was for unit testing React components, but it soon gained popularity. It has experienced infinite updates and has been used by many developers to test their cases.

Jest is used to test React components and back and front-end JavaScript applications. It’s a common misconception that Jest is a toolset rather than a framework, but this is untrue. Jest also comes with a Command Line Interface (CLI), which lets you carry out project-related commands straight from the terminal. It also offers a test runner, an assertion framework, support for mocking techniques, and many other helpful tools.

What does the term “Jest Framework” mean?

It is a well-known testing framework built on Jasmine and was created especially to test React and Native applications. The creator of Jest, Christoph Nakazawa, describes it as a framework for “delightful JavaScript testing,” Its main goal is to improve and streamline support for testing resource-intensive online apps.

In addition to unit testing, Jest can also be used for component testing. It tests every JavaScript-based part and application, including how web apps render in browsers. Jest has a major advantage over well-known test automation frameworks because it does not depend on any programs or applications created or distributed by a third party.

Consequently, it has emerged as one of the best automation test frameworks for JavaScript. 

Why Should You Test With the Jest Framework?

A few of the JavaScript testing frameworks and tools available on the market are Cypress, Chai, Mocha, Jasmine, and numerous others. Nevertheless, why precisely should you use Jest? Let’s get into the details of why you should test using the Jest architecture now:

• No configuration required

Jest only needs a basic setup and setting. It is one of the most uncommon test frameworks because it is one of the few that does not need a complex configuration to test apps.

• Mocking support

Almost every type of mocking is supported by the Jest design. Its many functions include functional and timer mocking for specific API calls.

• Built-in Code

Jest supports code coverage as part of its default implementation. It offers CLI-based commands ready to use right out of the package and delivers accurate code coverage to ensure an application’s or project’s overall effectiveness. One can use the Jest setup file’s collect coverage or coverage command. 

• Rich API

Jest offers to have a sophisticated API. It has a broad range of useful APIs, or application programming interfaces, that let you match and validate values and fulfill other conditions and specifications. The Expect API, which offers various matcher algorithms, is an example. These matcher functions can be utilized to validate particular numbers and situations.

• An extremely simple migration

Regardless of the tool or framework you have been using, you can switch to Jest at any moment without dealing with the typical programmatic issues related to your module. Thanks to the Jest-code mods, any testing system can be changed to Jest without undergoing unpleasant migration work.

• Secure

One of the labor-saving features Jest offers is the capability to run unit tests for numerous units simultaneously. Jest uses a queue to run each test one at a time. If any unsuccessful tests are in the queue, Jest will run those tests, then rearrange the queue depending on how long each test took to finish.

• Documentation:

The community’s help and the supporting documentation are both perfect. A pertinent real-world illustration is provided for each topic addressed in the documentation.

• In-built CLI

The command line tool with Jest provides code coverage right out of the box. The collectCoverage property, located in the Jest configuration file, controls this functionality. With the CLI, you have full authority over your test procedures and the testing process itself. Additionally, it has an interactive mode that can instantly run tests on recent commits.

• Pre-commit hooks

Pre-commit hooks are a feature of the Jest testing framework that allow you to execute only the test cases that are relevant to the current run or those that have altered since the last commit. To put it another way, pre-commit hooks let you run just the test cases that have been altered since the last commit. We are no longer required to wait for the conclusion of each and every other test instance. These tests, also known as snapshot tests, are advantageous in that they lessen the time and effort required to test for regressions

Important Features of Jest making it a perfect testing tool:

Here are some of the most significant features of Jest:

• Performance

Thanks to its scalable architecture, Jest was designed to work well with large and small initiatives. Because it performs checks in parallel, it will consistently be quick. It is simply not helpful to wait for a code base to be built before tests are frequently run, and it is not scalable for big projects.

Jest can carry out the tests and comment on whether they were successful. If any tests fail, Jest will provide in-depth information regarding the failure, including the anticipated and actual values. This will allow the user to investigate the problem and find a solution.

In a nutshell, unit testing is an essential component of the software development process. By writing and running tests with Jest, you can ensure your ReactJS components function as anticipated. This will help prevent bugs and other issues in your application.

• Snapshot testing

That’s right, capture a few pictures, and your test cases will be ready. 

Jest supports snapshot testing, which can be useful when working on React development projects to avoid inadvertent UI regressions. These tests take screenshots of the component structure after it has been rendered and then compare them to subsequent depictions. When they do not correspond, your test is considered to have failed, which indicates that something has been altered. If you anticipate this change, you can easily instruct Jest to refresh the snapshot.

When evaluating your React components, you can use a strategy very similar to this one. 

• Sandboxing and test isolation

There will never be a situation in which two different tests are incompatible, and there will never be a situation in which a module’s global or local state causes problems.

So let’s say there are three components in the react tree, and we are creating two to three test cases for each element, which could potentially cause a conflict. However, because we have test isolation and every test file is sandboxed, the execution of these test cases is uniquely handled. It is highly unlikely that interference between two cases will occur.

• Jest is as fast as light:

Undoubtedly Jest framework is too fast. For the tests that are CPU bound, the Jest can save a lot of time in running them. An example of one famous company known as Airbnb was seen switching from Mocha to Jest, allowing them to drop their test runtime from 12 minutes to just 4.5 min. The Local test took 45 minutes with them, but it dropped to 14.5 minutes with Jest.

How is the Jest framework working too fast? It is undoubtedly a combination of many factors:

• Caching babel: The factor reduces the CPU-intensive babel transforms, leading to fast working.
• The slowest tests are run first: It ensures that every core is used at its maximum ability.
• Parallelization: It is undoubtedly one of the features used by every other framework.

These features contribute a lot to making the Jest work faster and executing more tests simultaneously.

• Jest is known to be a one-stop-shop:

Jest comes with its in-built spies, and its own mocking library too. Jest is used with Jasmine, so it is inherited with all the good qualities of the respective framework. But in its recent updates, it is found that Jest has new features but works on the same functionality, yet added new improvements.

How can the LambdaTest platform be used to run Jest tests?

Platform like LmabdaTest allows the user to perform cross-browser testing on more than 40+ operating systems and browsers just to speed up the execution of the test. In other words, it will enhance the test coverage with the product quality. The LambdaTest provides smooth integration with Jest framework. The user can run their test scripts on the LambdaTest cloud platform. To start with the automated testing with use, the user must have a great internet speed and sign-up on the LambdaTest platform to start through. Do know that the LambdaTest platform is easy and free to sign-up.

Conclusion

Jest is a testing platform renowned for its quick setup and simplicity. Many other developers and organizations use it in addition to being actively developed and used by Facebook to test all their React apps. It is TypeScript compatible, has everything you need in a single, user-friendly program, and is the best option for testing React and React Native apps. Additionally, switching from different other testing options is quite easy with them.