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Jest and Puppeteer
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Getting started with automated testing using Jest and Puppeteer

There are significant distinctions between manual and automated testing, as most professionals in the software business are aware. Manual testing necessitates physical time and effort to guarantee that the software code performs as expected.

While automated testing takes care of itself, end-to-end. If you are considering automating your browser testing, Jest and Puppeteer can be a good idea. It is not only quick and reliable, but also provides a clear syntax that makes it easy to construct tests that everyone can understand. Let us proceed with reading this guide if you want to learn more about using Puppeteer to test the UI of your application.

Jest – what is it?

Jest is a testing tool that was developed by Facebook specifically for the purpose of testing React applications. It is also used for the testing of applications written in Babel, JavaScript, Node.js, Angular, and Vue.js, and it is compatible with NestJS and GraphQL.

Jest was developed with the goal of being as easy to use as possible. It provides a robust and aesthetically pleasing API for building isolation tests, snapshot comparison, mimicking, test coverage, and more.

Jest can be used to validate almost anything involving JavaScript, particularly web-application browser rendering. Jest is also widely used for automated browser testing, making it one of the most widely used Javascript testing frameworks. Jest also includes a combination of an assertion library, a test runner, and a built-in mocking library. It distinguishes itself through its simplicity, making it an ideal tool for testing JavaScript Library Projects such as AngularJS, Vue JS, Node JS, Babel, and TypeScript.

Using Jest Framework for Selenium JavaScript Testing

A few reasons to use Jest framework include better speed and performance, capabilities to carry pre-commit hooks, easy migration, along with some additional features like auto-mocking modules, setting coverage levels, and module mappers. The Jest framework also contains support for many projects running in the same runner, as well as customer resolvers like Babel and Webpack.

What is Puppeteer?

The Puppeteer framework for Node.js offers a user-friendly application programming interface (API) for interacting with Chrome or Chromium web browsers through the DevTools protocol. Puppeteer is set up to operate in a headless mode (where there is no visible user interface), but it is also capable of operating in a headful manner (where you see the UI of the browser). Are you curious about the capabilities of Puppeteer? Using Puppeteer, you can:

  • Scrape website pages
  • Automate form submissions
  • Monitor page loading performance
  • Make server-side rendered versions of single-page applications
  • Create screenshots
  • Develop testing automation
  • Create PDF from web pages

Puppeteer is used for testing on several browsers. Your website may be tested on all chromium-based browsers, such as Chrome, Microsoft Edge Chrome, and Chromium, with the help of Puppeteer. Because of the vast amount of people who use these browsers, it is essential that you ensure your website displays properly when viewed using these browsers.

You have the ability to test a variety of versions of each browser, ranging from the most recent browser release to the very first version that Puppeteer ever supported. At this time, Internet Explorer (IE), Firefox, and Safari (WebKit) are not supported as Puppeteer only interacts over the DevTool protocol. The only browsers that are supported are those that implement this protocol. We recommend making use of Selenium WebDriver if you are interested in testing on a variety of browsers. This supports a large number of browsers including mobile browsers, as well as desktop browsers. Or alternatively you can also switch to Puppeteer Recorder.

What is Puppeteer Recorder?

Puppeteer Recorder is a tool that comes pre-installed in Chrome that enables you to record your activities and save them as Puppeteer scripts. At this time, it is only accessible as an experiment inside the Chrome DevTools, and you may activate it by selecting the Recorder checkbox in the Settings > Experiments menu of your Chrome DevTools.

It’s simple to use the Puppeteer Recorder, and it’s an excellent method for rapidly generating Puppeteer scripts, that you can then arrange to perform automated processes on your own browsers or on a cloud-based grid such as TestingBot. Using the Puppeteer recorder also acts as a terrific way to save time.

Puppeteer Cross-Browser Testing

You can test your website with Puppeteer on all chromium-based browsers, including Chrome, Microsoft Edge Chrome, and Chromium. Because these browsers are used by several users, it is critical that your website behaves correctly in them.

You can test different versions of each browser, from the most recent to the oldest Puppeteer-supported version.

Safari (WebKit), Firefox, and Internet Explorer are not yet supported. Because Puppeteer only communicates via the DevTools protocol, only browsers that support this procedure are supported. In case, you want to test on other browsers, we recommend Selenium WebDriver. This works with all of the major browser vendors, including mobile browsers.

You can run also Puppeteer Jest test scripts online using cloud-based automation testing platforms like LambdaTest. By using LambdaTest, you can perform end to end testing using Puppeteer framework across over 50+ browsers and OS combinations faster. You can reduce test execution time by running Puppeteer tests in parallel on 50+ browsers and OS configurations at the same time. Also, release your products faster, with confidence, by reducing developer feedback times.

Using Puppeteer to debug the available choices

In addition, Puppeteer offers several extra debugging capabilities, which might be helpful for testing React applications from beginning to finish. Let’s go over some of these choices, and then we’ll go over how to add them to a test that’s already been created.

  1. Headless Mode: The headless mode of the Chromium web browser is loaded whenever Puppeteer is used. A browser that does not have a visible user interface shell but nevertheless provides the same functionality as a conventional browser is known as a headless browser. It is an excellent instrument for use in automated testing and in server setups.
  2. Slow mode: When headless mode is on, it’s not always easy to keep track of what’s going on in the real browser. For instance, the submission of forms occurs extremely quickly since the information is not being entered in by humans but rather by software that works practically instantaneously.
  3. Utilizing Jest Puppeteer as a Tool: Jest Puppeteer offers all of the settings that is necessary in order to execute unit tests with Puppeteer. This enables Puppeteer tests to be written with fewer requirements for setup and in a more straightforward manner.

Let’s get it set up fast so we can compare it to the strategy we’ve been using for the other tests and see how it performs differently.

When you use Jest Puppeteer, you won’t need to first construct the website for production and then serve it on a static server before running the test. This is one of the most significant benefits of utilising Jest Puppeteer. Instead, you may execute the test command in conjunction with a local development server that is already active. You only have to name the command and the port that you want to use.

As was just discussed, Jest Puppeteer simplifies the process of creating tests, which frees us from the obligation of launching a new instance of Puppeteer or generating a fresh page for each and every test suite.

Another modification is made to the way the form is filled out. You may use Jest Puppeteer to assert that a form will be filled as long as you have a selector for the form to be filled and its input fields have a name attribute. This is necessary for the assertion to be valid.

In addition, Jest Puppeteer makes it much easier to declare that a button will be pressed by making use of the button’s actual content. Therefore, we utilise it to assert that the button with the word “Submit” will be pressed in the test suites that were just described.

Jest applications using Puppeteer

Jest is a Javascript Testing Framework that was developed by Facebook. It facilitates straightforward testing for a variety of Javascript applications, such as Babel, TypeScript, React, Angular, and Vue, amongst others.

You are able to begin using Jest if your application is currently utilising NestJS or GraphQL, or any other well-known Javascript framework.

It has a quick installation and use time, a feature-rich application programming interface (API), and simple test mocking and snapshot features. Your tests may be performed in parallel using Jest, which also provides excellent error reporting and the ability to run tests in isolation.

There is a project that is known as Jest Puppeteer, and it enables QA professionals and software developers to execute tests that have been developed for Jest using Puppeteer. It includes special matchers that are suited to Puppeteer and goes by the name expect-puppeteer. Additionally, it makes it simple for you to execute your tests with Puppeteer. A Jest preset known as jest-puppeteer is made available by the project. This preset may be included in the Jest configuration file that you use (jest.config.js).

Bottom line

In conclusion, using Jest Puppeteer makes it possible to eliminate the use of selectors entirely, making it much easier to verify if a text is there on a page. Throughout the course of this lesson, we went through how to develop tests for React applications by using Jest as a building suite and Puppeteer for simulation such as typing in inputs, clicking, and other similar actions.

When it comes to testing React applications, a combination of Jest and Puppeteer is a choice that simply cannot be made in error. Since Puppeteer is currently being constantly developed, be sure to review the API reference in order to learn about its further capabilities.

Together, Puppeteer and Jest will be used to develop automated tests for an example web application that includes features for account creation and login. Your first setup Puppeteer and Jest so that they may function together, and then you built scripts to explore the user interface (UI) of the web application, returning the values of any HTML elements it found. Last but not least, you checked to see whether those numbers were consistent with the predicted values of the activities you were evaluating.

End-to-end testing is not just a helpful method for evaluating your user interface (UI), but you can also use it to ensure that other crucial components in your web application are operating as planned. If you want to conduct performance tests on many devices, for instance, you may utilise device emulation and network throttling to do this. Check out the Puppeteer and Jest official documentation online if you want to learn more about end-to-end testing.

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