The Role of Visual Testing in Modern UI/UX Development

The Role of Visual Testing
in Modern UI/UX
Development

Table of contents
What Is Visual Testing?
Who Uses Visual Testing?
Features of Visual Testing
Advantages of Visual Testing
1. Efficient cross-browser and cross-device testing
2. Improved regression testing
3. Enhanced user experience
4. Detection of visual bugs
5. Automation efficiency
Disadvantages of Visual Testing
1. False positives
2. Resource intensive
3. Difficult to set up and maintain
4. Tool limitations and dependencies
5. Limited detection of functional issues
Steps for Implementing Visual Testing
1. Define objectives and scope
2. Choose the right testing tool
3. Set up your testing environment
4. Integrate with the CI/CD pipeline
5. Configure and fine-tune your tests
6. Run initial tests and review the results
7. Establish a clear review process
8. Invest in continuous maintenance and updates
9. Document and educate
10.Scale and optimize

Visual Automation Testing Methods
1. Pixel-by-pixel comparison
2. DOM-based comparison
3. Layout comparison
4. Screenshot comparison
5. Visual regression testing
6. AI and Machine Learning (ML)-based testing
7. Perceptual comparison
8. Component-level testing
9. Cross-device and cross-browser testing
10.Manual visual testing
Visual Testing Tools to Know About
1. TestGrid.io
2. Applitools
3. Selenium
4. BackstopJS
5. Percy
Final Words

Modern web designers create app interfaces with the understanding that they will be viewed
across various browsers, devices, and operating systems. As a result, ensuring visual
consistency across all these platforms is a crucial aspect of website QA.
However, this can quickly become a mammoth task, especially if you’re testing for dynamic,
responsive content, which can load differently across different screen sizes and resolutions by
default. Luckily, there’s a process known as visual testing that can help.
Let’s talk about what that looks like in this short guide.
What Is Visual Testing?
Visual testing is a form of software testing that assesses the visual fidelity of your user
interface (UI) or graphical user interface (GUI). It evaluates the actual visible output of your
application against the expected results and thus helps you catch and fix “visual bugs” in a page
or screen.
Typically, these visual bugs tend to be missed by other types of UI tests, like functional tests. To
deliver a flawless webpage experience, you’ll want to invest in functional and visual testing.
You can conduct visual testing on individual components as well as on the application as a
whole. Several automated visual testing tools are available on the market that can enhance the
speed and accuracy of the process. Many teams now leverage cloud-based automation testing
to streamline their workflows, enabling them to execute test cases across various environments
seamlessly. We’ll discuss these tools later in detail.
Who Uses Visual Testing?
There are several people involved in ensuring that your visual testing happens smoothly and in
sync with other kinds of testing:
● Web designers: They verify that the app is suitably in line with their design concepts and
adheres to the brand guidelines.
● Front-end testers: They check that the app is visually consistent and responsive across
all browsers, devices, and screens.

● QA experts: They ensure that the entire app has design fidelity by meticulously
inspecting and validating its visual aspects.
● Manual testers: They check the UI for visual quality and highlight any design
discrepancies that might have been missed.
Features of Visual Testing
Here are the main components of any visual testing process:
● Testing UI elements: It verifies that UI elements like text fields, images, buttons, and
other graphical components are positioned exactly as they should be according to the
design.
● Testing theme and color: The app’s branding should comply with design guidelines, with
uniform appearance and saturation across devices.
● Testing text and fonts: Visual testers check that all content appears in the correct font
style and size and that all text is readable and formatted correctly.
● Design coherence: Visual testing ensures the app’s design and arrangement stay
consistent across different screen sizes and resolutions.
Advantages of Visual Testing
Along with functional testing and performance testing, visual testing has emerged as one of the
most valuable tools for ensuring that your app looks and behaves exactly as it should. There are
multiple advantages to investing in visual testing, including:
1. Efficient cross-browser and cross-device testing
Visual testing tools can automatically run tests on UI behavior across devices and browsers to
ensure that end users in all environments get a uniform and high-quality experience. The tools
are particularly useful for catching issues that only occur under specific conditions, such as a
glitch in image loading on an older model of iPhone.
2. Improved regression testing
Visual testing tools can quickly compare screenshots of your current UI with a defined baseline
to ensure that any UI changes you introduce don’t cause unintentional visual regressions.

Moreover, automated tools can adapt much faster to UI changes than traditional testing
scripts, making them more suitable for dynamic environments.
3. Enhanced user experience
Your end users will access the app from various platforms and expect a consistent experience
regardless of where they log in.
With visual testing, you can ensure that the UI is consistent across devices, operating systems,
browsers, and screen resolutions.
Moreover, visual testing focuses on the end user’s point of view, which means your testers
access the UI just like a user would and can accurately highlight any differences or glitches in
the navigation experience. This makes for a more polished app than one that has relied on
backend testing alone.
4. Detection of visual bugs
Visual testing helps you quickly spot visual issues like overflowing text, improperly rendered
color palettes, or images that are misaligned on iOS but look fine on Android. These aren’t
functional issues per se, but they can negatively affect the aesthetics of your app and create a
poor impression in the end user’s mind unless corrected.
5. Automation efficiency
With automated visual testing, chances of human error immediately go down. You can now
rapidly test thousands of pixels within a few seconds and be assured of the accuracy of the
results.
Moreover, when you integrate it into your CI/CD pipeline, your developers can instantly get
feedback on how the app’s visuals have changed with each code change, helping them detect
and fix any visual issues much sooner.

Disadvantages of Visual Testing
While visual QA testing has many benefits, it’s not without drawbacks. When you select a
visual testing tool, you’ll consider these factors.
1. False positives
Visual tests might sometimes flag false positives, such as minor rendering differences that
don’t affect the user experience. Investigating those can take up unnecessary time and
resources from your time.
Another area with the potential for false positives is dynamic content, such as date or time
stamps, which by default display different results each time. Your testing team will need to bake
in extra configuration for those elements.
2. Resource intensive
Running visual tests across different end-user environments can be highly resource-intensive,
which could potentially slow down your continuous integration and deployment (CI/CD) process.
Moreover, storing your baseline images and results can take up a lot of space, particularly with
complex UIs, which can further increase your overhead.
3. Difficult to set up and maintain
Setting up a visual automated testing framework can be costly and complicated as you
configure your testing environments and integrate the testing tool with your CI/CD pipelines.
Plus, as your UI evolves, you’ll need to keep upgrading the baseline designs, which can quickly
become cumbersome.
4. Tool limitations and dependencies
How effective your visual testing is depends almost entirely on which tool you’re using. Not all
tools are equally good at testing across diverse environments or handling dynamic content.
When introducing a visual testing tool, your team will also be involved in the learning curve. The
longer your testers take to become familiar with it, the more your processes will slow down.

5. Limited detection of functional issues
Automated visual testing focuses on your app’s appearance and won’t detect issues like
faulty data handling or workflow errors that don’t directly impact the UI. Therefore, you’ll need to
run visual tests alongside your functional testing methods.
Steps for Implementing Visual Testing
Implementing a sound visual testing process involves multiple steps, some of which might look
different depending on your development workflow. In general, though, these are the steps you
want to keep in mind:
1. Define objectives and scope
Start by determining exactly what you want to accomplish with visual testing. Are you looking to
ensure cross-browser consistency, detect layout issues, or verify that the site branding adheres
to the guidelines?
Then, select and prioritize the parts of your app that need visual testing, such as critical user
flows or UI components that often change, such as popups with the latest promotions.
Then, select and prioritize the parts of your app that need this type of testing, such as critical
user flows or frequently changing UI components, like popups with the latest promotions.
2. Choose the right testing tool
Do your research on the different types of testing tools available, and conduct trial runs to see
which one best fits your project environment. Evaluate them on criteria like cross-browser and
cross-device support, ease of use, CI/CD integration, ability to handle dynamic content, and so
on.
3. Set up your testing environment
Make sure your testing environment is ready to implement visual testing. Have baseline images
of your UI ready as a reference for visual tests, and keep them stored in version control along
with your code. This helps with tracking UI changes over time.

4. Integrate with the CI/CD pipeline
By integrating your visual tests with your CI/CD pipeline, you ensure that the tests are run
automatically with each code commit or pull request and can provide instant feedback on visual
regressions. In addition, consider investing in a tool that supports parallel testing across
multiple browsers and devices, saving you time.
5. Configure and fine-tune your tests
To avoid false positives, you’ll need to take some time to configure your testing tool for optimal
results. For instance, you can write custom scripts to stabilize dynamic elements like
timestamps before taking screenshots.
You can also set acceptable thresholds for visual differences, such as a small pixel difference
between a desktop and a mobile device.
6. Run initial tests and review the results
Perform your first round of visual tests, then use that to establish a baseline and identify any
issues that immediately pop up. Review everything carefully, and once you’re satisfied, add the
baseline images to storage for future comparisons.
7. Establish a clear review process
Collaborate with your developers, designers, and QA engineers to set up a clear process for
reviewing and addressing test failures and determining which issues require intervention. This
way, everyone is clear on the standards to be met and can resolve problems efficiently and
without too much back-and-forth.
8. Invest in continuous maintenance and updates
As your app evolves, you’ll need to update your baseline images to reflect any intentional UI
changes for maximum test accuracy. You’ll also need to review and refine your test
configurations and thresholds as necessary.
9. Document and educate
Be sure to document every step of the visual testing process so that all future testers follow a
consistent workflow.

You should also invest in training your team on best practices and how to interpret the test
results. This ensures that everyone on your team is invested in upholding visual quality and
consistency on the app.
10. Scale and optimize
It’s important to expand the scope of your visual testing automation as your app grows so that
you always prioritize the components that have the most impact on user experience. You should
also keep optimizing the testing process by reducing test execution time or enhancing your
parallel testing capabilities.
Visual Automation Testing Methods
Let’s take a look at the common techniques you should know about.
1. Pixel-by-pixel comparison
This is a method where the current screenshot of a UI is compared against a baseline image on
a pixel level. It’s highly precise, catching even the smallest differences in the UI’s visual
appearance.
However, Pixel-by-pixel comparison is also very sensitive, which means it might flag minor,
irrelevant changes, like rendering differences between browsers, as potential issues.
It works best for applications where maintaining pixel-perfect accuracy is critical, such as in
high-fidelity design environments.
2. DOM-based comparison
If you want to focus on the structure and layout of the web page by comparing the Document
Object Model (DOM), then DOM-based comparison is apt. Instead of looking at the rendered
pixels, it checks for changes in the layout and structure of HTML elements.
This method helps ensure that the overall layout remains consistent, even if minor differences in
appearance don’t affect the user experience. It’s particularly effective for testing applications
where the layout’s integrity is more important than exact visual matching.

3. Layout comparison
This technique checks whether UI elements are placed correctly relative to each other, ensuring
that the overall structure of the page is intact. Layout comparison is handy for responsive
designs, where the placement of elements can change based on screen size and orientation.
While it doesn’t scrutinize the content within the elements, it ensures that the design layout
adapts correctly across different devices.
For example, a retail website might use layout comparison to ensure that product grids and
navigation menus remain properly aligned when viewed on mobile devices, tablets, and
desktops.
4. Screenshot comparison
It involves taking screenshots of the entire page or specific components and comparing them
with baseline images. This method provides a comprehensive view of the UI’s visual state,
capturing everything from colors and fonts to images and layouts.
Screenshot comparison is easy to implement and widely supported by visual testing tools.
However, it can be resource-intensive and may require managing large amounts of image data.
A web app that frequently updates its user interface might use screenshot comparison during
its CI/CD process to detect visual regressions before the new code is deployed automatically.
5. Visual regression testing
This automated process compares the current version of an application against previous
versions to identify unintended visual changes.
Visual regression testing is highly effective when integrated into CI/CD pipelines. It provides
immediate feedback on visual issues as the application evolves.

For example, a large eCommerce platform might apply this technique to ensure that updates
to the checkout process don’t introduce visual errors, such as misplaced buttons or incorrect
color schemes, across different site versions.
6. AI and Machine Learning (ML)-based testing
Advanced visual automation testing tools leverage AI and ML algorithms to analyze visual
differences intelligently. These technologies help identify changes that significantly impact the
user experience while ignoring trivial variations.
Over time, the AI learns from past results, improving its accuracy. This method is beneficial for
reducing false positives and handling dynamic content more effectively, though it requires more
sophisticated tools and can be more expensive to implement.
A social media platform might use AI-based visual testing to ensure that user-generated content
is displayed correctly across various devices, filtering out minor rendering differences that don’t
affect usability.
7. Perceptual comparison
It compares images based on how they appear to the human eye rather than on a strict
pixel-by-pixel basis. Perceptual comparison focuses on visual differences that would be
noticeable to users, making it more aligned with human perception.
It helps reduce noise from insignificant differences and focus on changes that truly impact the
user experience.
8. Component-level testing
This method isolates individual UI components for testing in a controlled environment rather
than testing the entire application simultaneously.
Component-level testing is instrumental in applications built with reusable components. It
allows you to test each component’s visual integrity independently. It’s scalable and helps detect
issues early in the development process.

9. Cross-device and cross-browser testing
As the name suggests, this involves running visual tests across different devices and
browsers to ensure that the application’s appearance remains consistent. Cross-device and
cross-browser testing are essential for applications that must work seamlessly across various
environments.
For instance, a banking app might use techniques to ensure that its UI remains consistent and
functional on all supported browsers and devices, including older browser versions and
low-resolution screens.
Cross-browser and cross-device testing combine other visual testing techniques with browser
automation tools to achieve broad coverage, though it can be resource-intensive to maintain.
10. Manual visual testing
Despite the rise of visual automated testing, doing it manually also remains a valuable method.
Manual testing involves human testers manually inspecting the UI for visual defects. It leverages
human intuition and the ability to apply context-based judgment, making it possible to catch
subtle issues that automated tests might miss.
Manual testing is often used in conjunction with automated methods to provide a final quality
check before release.
For example, before launching a major update, a gaming company might employ manual visual
testers to review the game’s UI across different levels and screens, ensuring that the visual
experience aligns with the design intentions.

Visual Testing Tools to Know About
TestGrid.io
Are you looking for a robust automated visual testing solution for detecting even the slightest
deviations in the appearance of web pages and mobile apps? Look no further than TestGrid.io.
Our platform ensures pixel-perfect precision across various devices and browsers, making it
essential for delivering flawless user experiences.
With advanced testing capabilities, it streamlines visual testing, allowing you to efficiently
identify and correct any inconsistencies in your apps’ visual presentation.
One of the standout features of TestGrid’s visual testing is its seamless automation. You can
integrate this testing without the need for external SDKs or significant changes to your existing
functional test case code.
With just a few lines of code, TestGrid’s AI takes care of the rest, automatically generating visual
comparisons with baseline and subsequent tests. This built-in feature eliminates the need for
feature-specific tools.
Additionally, its Visual AI capabilities extend the scope of traditional visual testing by validating
every element within an interface, including text, images, layouts, and videos.
This approach ensures that the user interface looks correct on any device or screen size,
particularly in complex test scenarios like BFSI (Banking, Financial Services, and Insurance) and
eCommerce flows.
2. Applitools
Applitools is a well-known visual testing platform that uses AI to perform sophisticated visual
comparisons. It can detect meaningful visual differences using AI, reducing false positives. It
supports cross-browser testing and dynamic content handling and can be integrated into
various testing frameworks like Selenium, Cypress, and WebDriverIO.

While not open-source, Applitools Eyes offers a free tier for smaller projects and
open-source initiatives.
3. Selenium
Selenium is one of the most popular open-source tools for automating web browsers. It can be
adapted for visual testing through integrations with other libraries.
While it itself is primarily focused on functional testing, it can capture screenshots during test
runs, which can then be compared to baseline images using other tools like ImageMagick or
third-party libraries like SeleniumBase.
This capability makes Selenium a versatile option for teams that want to combine functional
and visual checks within a single framework.
4. BackstopJS
BackstopJS is a widely used open-source tool specifically designed for visual regression testing.
It captures screenshots of web pages and compares them against baseline images, highlighting
any visual differences.
It’s highly configurable, making it suitable for projects of all sizes. Users can define scenarios,
set custom viewports, and run tests in parallel to optimize performance.
5. Percy
Although not fully open-source, Percy provides a free tier and is often used in open-source
projects. It automates visual ui testing by capturing UI screenshots and comparing them against
previous versions, highlighting any visual changes that may have occurred.
It automates UI verification by capturing screenshots and comparing them to previous versions,
highlighting any visual changes that may have occurred.
The platform provides detailed visual diffs, allowing developers to identify and address visual
regressions quickly.

Final Words
In a world where apps are a dime a dozen and user expectations are increasing daily, visual
testing is a key asset for fine-tuning an app experience to be as delightful as possible.
Despite their drawbacks, automated visual testing tools can enhance your testing capabilities.
They let you continuously fine-tune the user experience and scale up to reach an ever-wider
audience.
As always, remember to keep checking in with your QA team so that they’re getting the most out
of the testing tool. You’ll soon be on your path to success.
Source: For more details, readers may refer to TestGrid.

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