Headless Browser Testing 101

April 9, 2024
5 min read
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Hello everyone! We’re back with a new blog post. This time we are not discussing any code. We will be presenting a new web browsing technique called the Headless Browser. Funny right? The name might seem weird, but it has good logic behind its name.

All of you must be aware of how important is the Web browser in today's era of the Internet. Web Browser is the primary tool for reading web pages and exploring the large internet. Can you imagine the internet without a web browser? NO, the Internet is useless without a web browser.

Headless browser is gaining popularity as the most viable option to test web apps. However, when using a Headless browser, you must be aware that whether for the current test strategy, it will really help to improve efforts or it will hinder them.

This blog post explains what headless browser testing is and which situations and use cases it supports. We will also discuss the limitations of Headless Browser Testing and the situations in which you should not use the Headless Browser.

What is Headless Browser?

Headless Browser is something that software test engineers are very fond of. As the name suggests, Headless Browser is a browser without a Graphical User Interface.

Unlike a normal browser, Headless Browser doesn't show webpages to the user and can pipe the contents to another program. When you start a Headless Browser, you won't be able to see the content on the screen because everything is running in the background.

Like a normal Browser, the headless browser is capable of parsing and interpreting web pages. In short, we can say the headless browser is capable of providing all the capabilities of a normal browser without taking a toll on system memory and speed. For example, the headless browser can cope without all sorts of downloads, parsing JavaScript and many more functionalities.

There are 2 ways to execute a Headless Browser:

  1. Via Command Line
  2. Using Network Communication.

One thing that headless browser lags behind is Web Surfing. Since Headless Browser doesn't have a Graphical User Interface, so these are not the suitable option for surfing the web, unlike the normal browser that is meant primarily for this task only. But once you finish reading this article, you will get to know that the Headless browser is a perfect choice for Testing Web Apps.

How can Headless Browser Testing be Useful?

  1. Automation: Headless Browser can be used to automate tasks, scripts and User Interface tests against a browser without requiring to start the browser as Headless browser can support automated control of webpages. Headless browser is also capable of automating web interactions like form submission, keyboard inputs, etc. The headless browser can enable up-to-date automated tests in a browser environment.
  2. Data Extraction: You may not want to navigate to the website and scrape it. It is more convenient to scrape a website headlessly. Just scrape the website and simply use the results to test multiple webpages as a part of the quality control effort.
  3. Layout Testing: Due to the quality of the Headless Browser to render and interpret CSS and HTML like a real browser, it can support a lot of layout checks. It is possible to test style elements such as page layouts, color selection for any elements, the font used, etc. It also supports tests for Javascript and AJAX execution. It is possible to automate screen captures for layout checks.
  4. Performance: If performance is a critical factor for you, then you are at the right place. A headless browser is your friend if you are conscious about the performance metric. But Why? How it helps? These questions must be coming to your mind. Let me explain to you.
  5. Headless Browser frees your system from the job of starting the Browser GUI.
  6. If you are doing the web page scraping, then you don’t need to navigate to the web page in order to execute scraping.
  7. After reading this, you must be wondering does this really helps? Yes, Of course, it helps a lot. Starting a browser GUI consumes a lot of memory in the system. Less memory consume means more speed and more speed means quicker results for the tests.
  8. For a developer, this is a lot of saving in time where they simply want to perform small smoke tests where GUI is irrelevant. For example, if a developer wants to check: Can he log into the application?
  9. The ability to perform tests via the command line saves a lot of time and effort.
  10. But do keep in mind that this is not the only factor that governs the performance. The performance also depends on the actual tests and the system under test.
  11. Miscellaneous: Apart from these categories, there are still some advantages that cannot be grouped into categories like:
  12. The headless browser supports monitoring network application performance.
  13. It is capable of generating screenshots and PDFs of web pages without actually starting the webpage in browser GUI.
  14. It supports running tests on a machine without the need to start the browser GUI.
  15. It also supports simulating multiple browsers on a single machine without causing the resource deadlock.

Limitations of Headless Browser Testing

  1. At the end of the day, real users are not using the headless browser. They are using normal browsers. So, you definitely don’t want to focus on bugs that happen in headless mode. In order to get real user experience and do functional tests, you need to mimic a real user and get exact feedback on what the user actually goes through while using the real browser. You want to observe the interaction between the user and the normal browser.
  2. Headless browser is a different concept from a normal browser in a sense that tests that will catch bugs and throw errors on a headless browser won’t find bugs on the real browser. Therefore, sometimes it becomes necessary to run tests on a real browser.
  3. If you want to do a lot of browsers debugging, then the headless browser is not a good option.

Thus, we can say Headless browser is a very good technique when you require fast feedback, want to test snippets of code fast and without a hassle to start a browser and also, they are quick to set up. But with all the advantages, like a coin, it also has 2 sides. The headless browser can be limiting if you want to do full GUI Testing or for the matter if you want to test all the varieties of the browser OS combination to ensure full test case coverage. For instance, debugging tools like video validation cannot be accessed in headless mode.

With this, we are done with Headless Browser Testing, a strategy that has both pros and cons. It is up to you to decide how to utilize it to its fullest power.

To know about Headless Browsing on CasperJS, click here.

Rupesh Garg
Rupesh Garg
CEO and Chief Architect
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