Thunderhead Speeds Quality Delivery with Applitools

4 min readFeb 16, 2021


Thunderhead is the recognised global leader in the Customer Journey Orchestration and Analytics market. The ONE Engagement Hub helps global brands build customer engagement in the era of digital transformation.

Thunderhead provides its users with great insights into customer behavior. To continue to improve user experience with their highly-visual web application, Thunderhead develops continuously. How does Thunderhead keep this visual user experience working well? A key component is Applitools.

Before — Using Traditional Output Locators

Prior to using Applitools, Thunderhead drove its UI-driven tests with Selenium for browser automation and Python as the primary test language. They used traditional web element locators both for setting test conditions and for measuring the page responses.

Element locators have been state-of-the-art for measuring page response because of precision. Locators get generated programmatically. Test developers can find any visual structure on the page as an element.

Depending on page complexity, a given page can have dozens, or even hundreds, of locators. Because test developers can inspect individual locators, they can choose which elements they want to check. But, locators limit inspection. If a change takes place outside the selected locators, the test cannot find the change.

These output locators must be maintained as the application changes. Unmaintained locators can cause test problems by reporting errors because the locator value has changed while the test has not. Locators may also remain the same but reflect a different behavior not caught by a test.

Thunderhead engineers knew about pixel diff tools for visual validation. They also had experience with those tools; they had concluded that pixel diff tools would be unusable for test automation because of the frequency of false positives.

Introducing Applitools at Thunderhead

When Thunderhead started looking to improve their test throughput, they came across Applitools. Thunderhead had not considered a visual validation tool, but Applitools made some interesting claims. The engineers thought that AI might be marketing buzz, but they were intrigued by a tool that could abstract pixels into visible elements.

As they began using Applitools, Thunderhead engineers realized that Applitools gave them the ability to inspect an entire page. Not only that, Applitools would capture visual differences without yielding bogus errors. Soon they realized that Applitools offered more coverage than their existing web locator tests, with less overall maintenance because of reduced code.

The net benefits included:

  • Coverage — Thunderhead could write tests for each visible on-page element on every page
  • Maintainability — By measuring the responses visually, Thunderhead did not have to maintain all the web element locator code for the responses — reducing the effort needed to maintain tests
  • Visual Validation — Applitools helped Thunderhead engineers see the visual differences between builds under test, highlighting problems and aiding problem-solving.
  • Faster operation — Visual validation analyzed more quickly than traditional web element locators.

Moving Visual Testing Into Development

After. using Applitools in end-to-end testing, Thunderhead realized that Applitools could help in several areas.

First, Applitools could help with development. Often, when developers made changes to the user interface, unintended consequences could show up at check-in time. However, by waiting for end-to-end tests to expose these issues, developers often had to stop existing work and shift context to repair older code. By moving visual validation to check-in, Thunderhead could make developers more effective.

Second, developers often waited to run their full suite of element locator tests until final build. These tests ran against multiple platforms, browsers, and viewports. The net test run would take several hours. The equivalent test. using Applitools took five minutes. So, Thunderhead could run these tests with every build.

For Thunderhead, the net result was both greater coverage with tests run at the right time for developer productivity.

Adding Visual Testing to Component Tests

Most recently, Thunderhead has seen the value of using a component library in their application development. By standardizing on the library, Thunderhead looks to improve development productivity over time. Components ensure that applications provide consistency across different development teams and use cases.

To ensure component behavior, Thunderhead uses Applitools to validate the individual components in the library. Thunderhead also tests the components in mocks that demonstrate the components in typical deployment uses cases.

By adding visual validation to components, Thunderhead expects to see visual consistency validated much earlier in the application development cycle.

Other Benefits From Applitools

Beyond the benefits listed above, Thunderhead has seen the virtual elimination of visual defects found through end-to-end testing. The check-in and build tests have exposed the vast majority of visual behavior issues during the development cycle. They have also made developers more productive by eliminating the context switches previously needed if bugs were discovered during end-to-end testing. As a result, Thunderhead has gained greater predictability in the development process.

In turn, Thunderhead engineers have gained greater agility. They can try new code and behaviors and know they will visually catch all unexpected behaviors. As a result, they are learning previously-unexplored dependencies in their code base. As they expose these dependencies, Thunderhead engineers gain greater control of their application delivery process.

With predictability and control comes confidence. Using Applitools has given Thunderhead increased confidence in the effectiveness of their design processes and product delivery. With Applitools, Thunderhead knows how customers will experience the ONE platform and how that experience changes over time.

Originally published at on February 16, 2021.




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