What is UI Testing? Definition, Tools, Best Practices

a comprehensive guide to ui testing


As technology advances at an unprecedented rate, the need for good UI becomes more critical than ever, and UI testing is the key to achieve it. A well-designed UI helps end users better accomplish their tasks, which contributes to better user experience, and ultimately user satisfaction. In this article, we will explore the concept of UI testing in-depth, real-life examples, popular approaches, processes, as well as top UI testing tools.

What is UI Testing?

UI testing is the process to validate both the functionality and visual aspects of the User Interface of an application. It focuses more on testing what the end users see and interact with instead of the inner workings on the backend.

It should be noted that UI testing is a much broader term than GUI (Graphical User Interface) testing. UI is all of the ways that a person interacts with a machine (including graphical and non-graphical ways), while GUI only counts the ways that involve the use of graphics on displays. From this perspective, testing how well a keyboard interacts with a website would be considered UI testing, but not GUI testing. 

Although UI testing and GUI testing are not technically similar, they are still used interchangeably because GUI is the most common form of UI for computers today. 


What is Mobile UI Testing?

Mobile UI testing is the process of testing the user interface (UI) of mobile applications to ensure they function as intended across various devices, screen sizes, operating systems, and also orientations. 

When doing mobile UI testing, QA teams usually pay close attention to:

  • Compatibility Testing: Ensuring the app works on different devices and operating system versions.
  • Responsive Design: Verifying that the app adapts to different screen sizes and orientations.
  • Gesture Testing: Testing touch gestures like swiping, tapping, pinching, and zooming.
  • Localization Testing: Ensuring the app works correctly with different languages and locales.
  • Performance Testing: Checking for smooth navigation and responsiveness.
  • Usability Testing: Ensuring the app is easy to use and navigate.


What is Web UI Testing?

Web UI testing involves testing the user interface of websites/web applications to ensure they are functioning correctly across various web browsers, screen sizes, and resolutions. The focus is on verifying that the web application's UI elements, such as buttons, links, forms, and navigation menus, work as expected and provide a consistent experience to users.

When doing web UI testing, the focus is slightly different. Several important testing types include:

  • Cross-Browser Testing: Ensuring the app works across different web browsers (e.g., Chrome, Firefox, Safari, Internet Explorer).
  • Responsive Design: Verifying that the app is responsive and displays correctly on different devices.
  • Form and Input Testing: Testing form validation, data entry, and submission.
  • Navigation Testing: Ensuring smooth navigation between different pages and sections.
  • Accessibility Testing: Verifying that the app is accessible to users with disabilities.
  • Performance Testing: Checking page load times and overall performance.

What UI Elements Do We Need To Test?

Here is a basic checklist to items to test when performing UI testing:

  • Buttons: Clickability, event triggering, styling, and accessibility.
  • Input Fields: Data entry, validation, error handling, and accessibility.
  • Dropdown Menus: Options display, selection behavior, interaction, and styling.
  • Radio Buttons and Checkboxes: Selection, default selection, interaction, and styling.
  • Tabs and Navigation: Navigation, active state, and content display.
  • Menus and Contextual UI: Visibility, interaction, options, and accessibility.
  • Notifications and Alerts: Display, timing, interaction, and styling.
  • Forms and Validation: Completeness, validation messages, error handling, and styling.
  • Images and Multimedia: Display, responsiveness, accessibility, and interaction.
  • Layout and Responsiveness: Alignment, responsiveness, and adaptability to different screen sizes.

Benefits Of UI Testing

Incorporating UI testing in the development process, especially early on, has several important advantages:

  • Improved User Experience: Interactive issues such as non-responsive buttons or misdirecting links usually impact a small area of the app or website, but they still confuse the user. If these issues occur at critical pages built to bring in new customers or sales, the bottom line is directly affected. UI testing prevents these issues from happening.
  • Enhanced Product Quality: A good application or website must not only deliver its expected functionality but also has visually-appealing components. UI testing uncovers bugs that directly affect the end user, and from these bugs testers can provide valuable insights to optimize and improve the overall app design.
  • Consistent Branding and Design: As the customer-facing part of an application, all parts of the UI must follow certain design guidelines to best communicate the values that the brand pursues. While looking for UI issues, testers can also make recommendations to improve design consistency throughout the app.
  • Increased Usability and Accessibility: Usability is about how easy-to-use the application or website is, while accessibility is the level of user-friendliness for people with disabilities. Both of these aspects strive to make the app more intuitive and inclusive. 

Common UI Bugs

  • Layout and Formatting Bugs:
    • Elements appearing off-center or misaligned.
    • Overlapping elements causing visual clutter.
    • Inconsistent spacing between elements.
    • Text getting cut off or truncated.
    • Content extending beyond container boundaries.
  • Functional Bugs:
    • Buttons or links not responding to clicks.
    • Broken or incorrect hyperlinks.
    • Issues with form submission or validation.
    • Navigation not functioning as intended.
    • Missing or misleading error messages.
  • Rendering and Visual Bugs:
    • Images failing to load or broken image placeholders.
    • Inconsistent font styles across different elements.
    • Colors not matching the specified design or brand guidelines.
    • Blurry or pixelated graphics or icons.
    • Improper alignment of icons or images.
  • Input and Interaction Bugs:
    • Unresponsive input fields or buttons.
    • Validation errors not displaying correctly.
    • Unexpected behavior when entering specific input formats.
    • Slow or laggy interactions with UI elements.
    • Disabled or inaccessible interactive elements.
  • Cross-Browser and Cross-Device Compatibility Bugs:
    • UI elements rendering differently across browsers.
    • Layout or UI issues on different screen sizes or device orientations.
    • Incompatibility with older browser versions.
    • Problems with touch-based interactions on mobile devices.


Types Of UI Testing

There are several ways we can categorize our UI testing activities:



Functional Testing

Test the functionality of UI elements to see if they work as expected.

Visual Testing

Test the visual aspects of the UI, including:

  • Overall visual design and aesthetics
  • Layout and alignment of UI elements
  • Color schemes and consistency
  • Typography and font styles
  • Graphical elements and icons
  • UI component styling (buttons, input fields, checkboxes, etc.)
  • Visual responsiveness across different screen sizes and resolutions
  • Visual consistency across different browsers and platforms

Usability Testing

Manually interact with the UI to see how easy-to-use and intuitive it is from the end-use perspective. Aspects to consider include:

  • Ease of navigation
  • Clarity of instructions
  • Areas of optimization to help users accomplish their desired task faster

Accessibility Testing

Test to see how accessible the UI is to users with disabilities, including:

  • Keyboard accessibility
  • Screen reader compatibility
  • Color contrast
  • Alt text for non-text elements
  • Image and video formats

Cross-browser Testing

See how the UI is rendered across different environments, including:

  • Browsers (Chrome, Firefox, Safari, etc.)
  • Operating System (Windows, macOS, iOS, Android)

These environments change the UI in their:

  • Layout (due to screen size differences)
  • Color
  • Functionality (certain features work on one browser but not on another)


Approaches To UI Testing

Similar to any other types of testing, there are 2 major ways to do UI testing: automated testing and manual testing.

Automated UI Testing vs manual UI testing

Automated UI Testing

Automated UI testing involves using automated test scripts to perform interactions with the UI. The human tester only needs to execute the script and interpret the results. 


  • Automated UI testing helps testers execute large numbers of tests quickly and quickly, saving a lot of time and effort compared to doing everything manually.
  • Automated scripts follow the sequence of actions precisely, minimizing the risk of human errors while ensuring reliable test results.
  • Test execution at scale enables QA teams to achieve higher test coverage (i.e. test more UI components, scenarios, or data variations). This means they will be able to uncover more defects and ensure comprehensive testing of the entire UI.
  • Automated UI testing unlocks a new level of UI regression testing, where tests are repeatedly executed to validate that the UI was not affected when app updates are introduced.
  • Automation testing for user interface frees up resources, allowing QA teams to scale the testing project, accommodating complex test scenarios or even multi-platform testing.


Automation testing is not without its challenges. With UI testing in particular, automated testing carries certain risks:

  • Automation testing requires the team to put initial effort into either developing an automation testing framework in-house to support automation needs of the team or finding an automation testing tool from external vendors with features that fit what the team needs
  • Developing robust and reliable test scripts, especially for complex UI components, require technical expertise. A common challenge with UI automation testers are dynamic UI elements, such as eCommerce cart icons. These icons constantly change when customers add a new item to their cart, so it can be challenging to define a “faulty” icon. 
  • When changes are made to the UI, existing test scripts must also be updated accordingly to ensure accurate test results. For large-scale projects with a large number of test cases, this is an extremely resource-intensive task.
  • Automated test scripts follow a set of predefined steps, and therefore can only “check” if an element can perform a certain action. There are many subtle UI issues that the testers didn’t even know existed in the first place, leading to missing issues.

Read More: Top 15+ Best Automation Testing Tools

Manual UI Testing

Manual UI testing involves a human tester manually performing interactions with the UI without the help of any tools or test script. They have to do everything from planning for what to test, design the test case, perform the actual testing, and document the results. Certain supporting technologies such as Google Sheets can be leveraged to help them accomplish those tasks faster, but the core activity - testing - must be done manually.


  • Manual testing for UI is more flexible, allowing testers to adapt to changes such as dynamic elements
  • Manual testing allows testers to add context, intuition, and human judgement to the testing process, helping them catch more obscure bugs that automated testing could have missed.


  • Time-consuming, especially for complex applications or repetitive scenarios
  • Risk of human error and subjectivity
  • Limited scalability because the larger the testing project, the more human testers is required
  • Lack of standardization since each human tester approach the same test case differently, which may produce different results

Read More: From Manual To Automation Testing: 5 Essential Steps

Popular UI Testing Tools And Frameworks

1. Selenium - Open-source Automation Testing Framework

selenium open source testing tool

Selenium is a well-known open-source framework used for automating UI tests. It is widely used in the testing industry and can automate test scripts on different operating systems like Linux, Mac, and Windows, as well as various browsers such as Chrome, Firefox, Internet Explorer, and Headless Browsers. Although it is extremely versatile and can be used for any purposes, Selenium requires a lot of coding expertise to fully leverage its power.

Key features:

  • Supported programming languages: Java, C#, Python, JavaScript, Ruby, PHP, and more.
  • Supported browsers: Chrome, Firefox, IE, Microsoft Edge, Opera, Safari, and more.
  • Parallel and cross-browser executions allow for testing on local or remote machines, speeding up execution and expanding test coverage.
  • Integrates with leading CI/CD tools and other testing frameworks.

2. Katalon - AI-powered Visual Testing Tool

Katalon logo

Katalon is a comprehensive quality management platform that simplifies all aspects of UI testing. Built on Selenium itself, Katalon gives you all the features you need to find bugs on the UI in a single platform, with extra AI-powered features. 

Read more: Katalon vs Selenium - Which is better?

Katalon AI Visual Testing can detect and capture the critical UI elements of your application, then create a baseline image to compare against. It can also detect and highlight dynamic regions of the application such as banners or pop-ups. These regions will not be flagged as bugs even if they change during tests.

What’s better is that Katalon allows teams to test across a wide range of devices and browsers. Instead of investing in tons of physical machines, teams can allocate their resources to more critical areas. After testing, Katalon generates detailed analytics and reports for improved decision making.

Katalon is great because it lets teams test on different devices and browsers without needing many physical machines. This allows teams to focus their resources on more important tasks. Katalon provides detailed analytics and reports after testing, which help with making better decisions.

Key Features:

  • One central platform for both functional and visual testing
  • AI-powered features like Layout Comparison and Text-to-text Comparison
  • On-cloud test environments available for a wide variety devices
  • Self-healing capabilities to automatically maintain automated visual tests
  • Easy integration with CI/CD pipelines such as Jenkins, GitLab, and Bamboo


Start UI Testing With Katalon

3. Cypress

Cypress for UI Testing logo

Cypress is an automation solution specifically designed for web testing. It focuses on supporting JavaScript frameworks. With its unique architecture, Cypress can run alongside your application in a browser, giving direct access to elements and faster execution during testing.

Key features:

  • Easily captures test snapshots.
  • Efficient debugging and step-by-step test execution using popular developer tools.
  • Controls network traffic, timings, server responses, and function behavior.
  • Accesses a dashboard service to enhance test performance.
  • Offers real-time support.

Read More: Katalon vs Cypress: A Detailed Comparison

Examples of Test Cases For UI Testing

Let’s say that we have an application for personal finance helping users with budget management and income tracking. This app is available on Android and iOS. Here are several example UI test cases for this app:

  1. Verify that the UI allows users to create new budgets by entering a budget name, duration (monthly, weekly, etc.), and allocated amount.
  2. Test that the UI enforces validation rules for budget creation, such as not allowing negative or zero amounts and ensuring a unique budget name.
  3. Test the UI's ability to allow users to edit existing budgets, including changing the allocated amount, duration, or budget name.
  4. Verify that the UI properly updates the budget details and reflects the changes in the budget overview and any associated reports or graphs.
  5. Verify that the UI allows users to add income details, such as amount, source, and date, for accurate income tracking.
  6. Test that the UI handles different types of income sources, such as salary, freelance income, or investment returns, and properly updates the overall financial summary.
  7. Test the UI's notification system for budget-related events, such as approaching budget limits, overdue expenses, or upcoming payment reminders.
  8. Verify that the UI properly displays notifications, sends reminders, and allows users to customize their notification preferences.
  9. Verify that the login page is displayed correctly with input fields for username and password.
  10. Test that the UI properly handles login attempts with valid and invalid credentials, displaying appropriate error messages.
  11. Validate that the "Forgot Password" and "Remember Me" options function as expected.
  12. Test the UI for the registration form, ensuring that all required fields are present and labeled correctly.
  13. Verify that the UI enforces proper validation rules for fields like email address, password strength, and phone number format.
  14. Test the form submission process, checking that user data is captured accurately and stored securely.
  15. Validate that the navigation menu or sidebar is properly displayed with correct menu items and hierarchy.
  16. Test that the menu items lead to the corresponding pages or sections of the application.
  17. Verify that the active menu item is highlighted or visually differentiated to provide clear navigation feedback.
  18. Test various input fields (text fields, dropdowns, checkboxes) to ensure proper validation.
  19. Verify that the UI displays error messages when invalid or incomplete data is entered.
  20. Test input fields with special characters, long strings, or boundary values to validate data handling.

UI Testing Best Practices

  • Apply shift-left testing approach and conduct UI testing team right from the early stages of the development process. This allows for early identification of UI issues and immediate troubleshooting instead of waiting until the very end of the sprint to start fixing.
  • Clearly articulate what aspects of the UI will be tested, what functionalities need to be validated, and what user experience considerations should be taken into account in the test plan.
  • Aim for comprehensive test coverage by considering various dimensions of UI testing, such as functionality, usability, responsiveness, accessibility, and compatibility. Cover both positive and negative test scenarios to ensure thorough coverage.
  • Use consistent and representative test data to test the UI's ability to handle different scenarios and edge cases while also increasing test coverage
  • Leverage test automation tools and frameworks to automate repetitive UI tests. This helps increase test efficiency, enables faster feedback cycles, and allows for regression testing as the UI evolves over time.
  • Cross-browser and cross-device testing is a crucial part of UI testing if you have a user base with diverse ensure the UI functions correctly and appears consistent across different web browsers, operating systems, screen sizes, and orientations. Consider the most popular browsers and devices used by the target audience.


UI Testing Checklist

FAQs For UI Testing

1. What is the difference between UI Testing and GUI Testing?

UI Testing is a more comprehensive term than GUI testing. While UI testing involves testing for both graphical and non-graphical elements, GUI testing only involves graphical elements

2. What are the key differences between UI testing and UX testing?

UI testing primarily focuses on the functionality, appearance, and behavior of the user interface elements. UX testing, on the other hand, focuses on the overall user experience, encompassing not only the UI but also factors like usability, user satisfaction, and the emotional response of users.

3. What is UI and API testing?

API testing is another type of testing with a completely different scope. It focuses on testing the functionality, performance, security, and reliability of APIs, which allow different software applications to communicate and interact with each other through data exchange. Together UI and API testing forms a quite comprehensive testing strategy, ensuring that both the front-end and back-end of an application works together seamlessly.


Start Testing With Katalon