What is user interface testing (UI testing)?

Scope of UI testing

UI testing can cover a wide range of verification:

• Functional correctness of UI elements: Verify that clicking a button triggers the expected action, that form input works correctly, that navigation between screens is as intended.
• Appearance and layout (Layout testing): Verify that interface elements are correctly positioned, aligned, do not overlap, and maintain responsiveness on different screen sizes.
• Visual regression testing: Comparing the appearance of an interface with a previous version or design pattern to detect unintended visual changes.
• Usability testing: An assessment of how easily and intuitively a user can use an interface to achieve their goals (although full usability testing often requires the involvement of real users).
• Accessibility (Accessibility testing): Verifying that an interface is accessible to people with various disabilities, according to accessibility standards (e.g. WCAG).

Manual vs automated UI testing

UI tests can be performed both manually and automatically:

• Manual UI testing: the tester manually “crawls” through the application, executing test scenarios, verifying the appearance and performance of interface elements. This method is flexible, good for exploratory testing and usability evaluation, but time-consuming, repetitive and prone to human error, especially for regression testing.
• UI automated testing: Specialized tools are used (e.g. Selenium, Cypress, Playwright for web, Appium for mobile) that simulate user interactions with the interface (clicks, text entry) and verify the state of the application. Automation is ideal for regression testing and checking key flows, but creating and maintaining stable UI tests can be difficult and expensive.

The place of UI tests in the test pyramid

UI tests are at the top of the pyramid of automated tests. This means that they should be relatively few in number compared to unit and integration/API tests. UI tests tend to be slower to execute, more fragile (prone to interface changes) and more difficult to maintain. Therefore, it is recommended to automate at the UI level only the most important business scenarios (end-to-end), and test most logic at lower levels (unit, API).

UI testing challenges

UI testing, especially automated testing, comes with some challenges:

• Test fragility: Even minor changes in HTML structure, CSS or element identifiers can cause automated UI tests to stop working.
• Time-consuming to execute: UI tests are much slower than unit or API tests.
• Environment dependency: Require a stable test environment with a running application and its dependencies.
• Maintenance complexity: Test scripts require regular updates and maintenance.
• Difficulties in testing dynamic interfaces: Testing modern dynamic interfaces (e.g. SPA – Single Page Applications) can be more complicated.

Summary

User interface (UI) testing is an important part of the quality assurance process, focusing on verifying the appearance, performance and usability of what the end user sees. It can be performed manually or automatically. UI test automation is valuable for regressing key flows, but should be used in moderation, complementing faster and more stable tests at lower levels of the pyramid.