Introduction to Selenium Headless Browser Testing 

Selenium WebDriver’s UI automation relies heavily on web browsers. An essential component of web automation testing is opening a browser and running the test cases on it. But if we run Selenium tests on any of the browsers, we frequently run into issues like poor browser rendering, clashes with other software programs, etc. In addition to this, the majority of CI systems nowadays are Non-UI (such as Unix-based systems). As a result, in order to run the test cases on those systems, we need a way to do so without displaying any user interface. This is where the headless browser comes into play, which facilitates the execution of the test cases and helps in the execution of the Selenium Headless Browser tests in a Non-UI mode.

Almost all modern browsers provide the proficiency to run them in headless mode. A good online Selenium certification course will explain further the concepts of Headless Browser testing.

What is a headless browser?

Programs that simulate browsers but do not have a graphical user interface are referred to as headless browsers. These applications run just like any other browser, but they don’t show any UI. When Selenium tests run, they do so in the background of headless browsers. The ability to run modern browsers headlessly is offered by almost all of them.

So, is Selenium capable of headless testing? Yes, headless testing is supported by Selenium. In earlier Selenium versions, the HTMLUnitDriver, a headless driver offering a Non-GUI implementation of Selenium WebDriver, was mostly used. However, Selenium now supports headless versions of actual browsers like Chrome, Firefox, and Edge with SeleniumWebDriver 3 and SeleniumWebDdriver 4. Selenium offers a number of options that allow us to use these browsers in headless mode. Let’s first examine the advantages of running tests in headless mode before delving into the specifics of these configurations.

Why use a headless browser for test execution?

The advantages of running a Selenium test case in headless mode include:

Useful in CI pipeline: It is not always viable to install genuine browsers on such distant workstations when we need to run automated test cases remotely on a server or in any of the build and release pipelines for continuous integration servers like Jenkins. We can efficiently execute automation tests using headless browsers.

Web scraping advantages: Headless browsers are the ideal solution when you want to create a web scraper or data extractor that must visit various websites and gather data. In these situations, we don’t worry about functioning, thus we browse websites to receive the information.

Support for various browser versions: On occasion, the tester may wish to replicate various iterations of the browser on the same computer. The majority of them allow for the emulation of various browser versions, thus in that situation, you would want to use a headless browser.

Executing automation tests more quickly: When compared to real browser automation, performance using a headless browser is better. It takes a long time for genuine browsers like Google Chrome, Firefox, and Internet Explorer to open and render HTML, and load CSS, JavaScript, and images. Headless browsers can begin operating right away without waiting for a page to fully load because they don’t need all of this to load. In headless browsers, we might reduce time when we need to execute regression scripts because they are much faster and can render results quickly.

Multi-Tasking: Utilise headless browsers to multitask. While the tests are running in the background, you can do whatever else with your browser or computer. Spend less time staring at the screen than we would otherwise.

Although running the Selenium test offers many advantages, there are also certain restrictions associated with it. The following is a list of a few of them:

Limitations of Headless browser testing

• Debugging will not be possible because taking screenshots and verifying the output are the only ways to see what is happening in the browser.
• Since the website does not render precisely with all the dependencies that it will render in an actual browser, headless browsers cannot accurately simulate user behaviour.
• While running the tests in headless mode, cosmetic bugs like the colour or placement of a web element may be missed.

How can you execute headless Selenium test cases?

According to what was previously described, Selenium WebDriver offers a number of drivers and configurations that make it possible to run Selenium test cases in headless mode. Let’s examine a few of them in the parts that follow:

• Utilising HTMLUnitDriver to execute Selenium test cases.
• Using a headless Chrome browser to execute Selenium test cases.
• Additionally, running Selenium test cases through a headless Firefox browser.
• Using a headless Edge browser to run Selenium test cases.

Conclusion

As a conclusion to the introduction, A browser simulation program without a user interface is known as a headless browser. Performance is one of the key advantages of adopting headless browsers. Headless browsers are quicker than traditional browsers since they lack a GUI. Using HtmlUnitDriver, Selenium offers headless browser testing. To learn more about Headless Browser testing, check out the online Selenium training.