What is Visual testing?

In this article, we will learn about a type of software testing known as Visual Testing. We will investigate the various subjects surrounding this testing approach and how we at Q-Pros adopt its various methods to guarantee excellent results.

What is Visual testing?

“Visual Testing” is observing an application’s visible output while monitoring for visual bugs and assessing the output in comparison to what is expected by demand.

Examining an application’s interface is done during the production period by developers, and later end-to-end users (a person who intend to use a product) will seal the deal with the product in the final stages.

The front-end developer’s main concern is to make sure that an application looks good on all browsers and devices with no obvious defects in terms of appearance. HTML and CSS as well as JS are interchangeable and can behave differently from one platform to another. This causes the risk of errors that not only affect appearance but also the functionality.

Considering such concerns, Visual testing is highly demanded by clients as a major step in QA (Quality Assurance).

The distinct value of Visual Testing

Testing your application’s script and making sure each input delivers an expected output on a basic level is not enough. Changes regarding layout and interface could occur due to a lack of compatibility.

Certain elements such as height, width, background color, font style, font size, and position within screen coordinates could change from one platform to another. This change is a result of different operating systems using various rendering methods.

Developers need to have their code written in a way that includes all previous versions of script input. Tools such as Babel could ease up the process by re-writing a code to make sure it could be rendered by all browsers in the same way. Cross-browser testing is a different approach with similar objectives. It includes other aspects than visual ones and focuses on how an application behaves in various browsers, making sure an application is operating based on business requirements and has achieved the desired quality level on all available browsers.

Manual Visual Testing Vs Automatic Visual Testing

Manual Visual Testing

Manual Visual Testing involves testing an application by sheer observation through usage and excavating any notes or anomalies that might stick out. This form of testing is becoming less popular because it is time-consuming.

To put it in perspective, testing an application “manually” will require testing it on all available browsers, in all operating systems, and taking into consideration, available devices and different screen configurations and screen displays. This will take a lot of time to accomplish, and it will open room for false readings.

Automated Visual Testing

In Automated Visual Testing, developers use tools and software to automate the test process and compare visual elements across different screen combinations.

Automated tools such as Selenium or Appium ease the process by running the script and creating UI variations.

As good as it may seem to have all screen combinations generated automatically, it still leaves the burden of testing it yourself to check for any bugs or defects.

One way to make things even easier is to rely on a method called Snapshot Testing.

In short, Snapshot testing creates a bitmap of multiple screen combinations and compares pixels, reporting/highlighting any unexpected changes in color hex code.

By comparing each pair of pixels in combination A & combination B, a snapshot test highlighted the difference as shown in the third table.

The Issue with Automated Visual Testing and The Snapshot Method:

As good as it may seem, Automated Visual testing is not perfect. While companies are relying on automated means of visual testing, the need for manual observation is essential.

Rendering will always cause deference – Relying on an algorithm to detect differences is almost redundant, as the algorithm will always report bugs. This is because pixels do not represent visual elements. Certain rendering activities include algorithms that create pixel differences to run a script.

Encountering some differences on a UI level does not always translate to bugs – some operating systems/browsers adjust CSS codes in a way that is seen as suitable. For Example, Minor changes may occur to the text based on the browser being used.