The importance of graphical non-regression tests and how to perform them

    4 Minutes Read

    When interacting with your application or website, the first thing your users notice is its visual appearance, and first impressions count!

    Visual perfection in user interfaces is now expected by consumers and must be monitored by quality assurance teams to protect brand image.

    Graphical non-regression testing (otherwise known as visual non-regression testing) is a way to ensure that you're delivering the best possible user experience from a visual perspective, and in this article we'll explore what it is, why it's important, and how to do it.



    What is a graphical non-regression test? 

    Non-regression testing is a technique used to verify that a new or modified feature works correctly assuming that the previous feature has not been affected.

    The advantage of this type of testing is that testers only check what has been changed, instead of the entire product, saving time and resources. The objective of non-regression testing is to see if undesirable behavior emerges as a result of the most recent software changes.

    The graphical non-regression test applies this same logic to the visual aspects of the software.

    Testers check to see if the most recent code changes have broken any aspect of the software's visual interface by comparing screenshots taken before and after the code changes.

    Even minor changes can have unforeseen consequences or cause new bugs to appear.

    Ultimately, the goal of visual non-regression testing is to ensure that the user experience is visually perfect by verifying that the layout and visual elements match expectations.


    Why are graphical non-regression tests important?

    Graphical non-regression testing is important to prevent costly visual bugs from negatively impacting the end user.

    Visual bugs negatively affect the user's visual experience when using software, and in many cases, these bugs can lead directly to lost sales and a compromised brand image.

    For example, suppose a user opens a website and wants to click a button, but cannot do so because an ad covers the button.

    The user is naturally irritated and wonders how such an obvious problem escaped the web developers, and they will associate this brand with a frustrating user experience.

    They may think, "If they can't even do these obvious things right, why would I want to buy any of their products or services?"

    There are hundreds, if not thousands, of device-browser-operating system combinations

    In today's world, there are a seemingly endless number of device-browser-operating system combinations that adopt "code-to-pixel" conversations in their own way. 

    Differences in screen sizes and resolutions must also be taken into account.

    The same software may look different (or be garbled) on different devices, and increases the importance of performing graphical non-regression tests.

    Don't functional tests catch visual bugs? 

    Functional tests are effective in detecting a variety of bugs, but not visual bugs. In fact, your website or application may pass all your functional tests, but still have visual bugs. Moreover, some tests are not really necessary such as checking a page base or the presence of a breadcrumb trail.

    To prevent these unwanted anomalies from flying under the radar, it is necessary to perform visual non-regression tests.


    How do automated graphical non-regression tests work?

    Graphical non-regression testing works by taking screenshots of the UX before a change is made and comparing it to a screenshot taken after the change with the help ofan automated testing tool

    To do this, developers first create code that replicates the user functions and place the controls at the appropriate points in the code to take a screenshot.

    The first time the test code is run, an initial set of screenshots is saved to serve as a reference against which all subsequent changes are compared.

    After defining the baseline, the QA runs the test code in the background, and whenever a change is identified, a screenshot is taken.

    Each screenshot is compared to the reference image corresponding to that particular section of the code and software. If differences appear between the images, the test is considered to have failed.

    Once the test code fully executes, a report is automatically generated, and a reviewer then examines all images diagnosed as changed from their baseline.

    If there are bugs that cause these image differences, the developers can fix them and rerun the test to see if the fixes worked.

    If changes to the user interface result in discrepancies, developers will need to review the screenshot and update the reference images against which visual tests can be run in the future.

    Can you do the graphical non-regression tests manually?

    Developers can take time after each new change to manually scan the pages for visual defects.

    However, this method is slow and complicated to do for an entire application or website, not to mention human error.

    That said, manual testing done in this manner can allow for ad hoc or exploratory UX testing, especially in the early stages of development.



    Implementing automated graphical non-regression testing - step by step

    Automating visual non-regression testing saves time, reduces the risk of human error and ensures the visual appeal of the software.

    For visual non-regression testing, you will need:

    • A tester to write and run tests.
    • An automated testing tool to replicate user actions.

    1. Create your test cases 

    Define what should be captured in the screenshots and at what point in the test they will be taken.

    This is where you ensure that these scenarios include a variety of user interactions that replicate what the software will have to handle in the real world.

    2. Use your automated visual testing tool to compare recent screenshots

    This step consists of comparing recent screenshots (captured after the most recent code changes were implemented in the software) with those captured earlier.

    The tool will generate a report detailing all differences detected between two sets of screenshots.

    3. Check the results

    One or more testers check and report whether the changes introduced have led to the expected results or whether disturbances have occurred.

    4. Fix bugs if needed and update the baseline

    If bugs are found, fix them (or send them to the relevant developers to be fixed). Once this is done, update the new screenshot as a reference for future visual testing.


    Mr Suricate | Graphical non-regression testing made easy with no-code automation

    Checking the visual aspects of your user experience is crucial to protect your brand.

    A no-code test automation platform like Mr Suricate facilitates these checks so you can ensure visually perfect user journeys in the most efficient way possible.


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