Answer.

Testing complex UI components is one of the most challenging tasks in automation.

Background: With the development of frontend, the emergence of SPAs, drag&drop, dynamic tables, and responsive UIs, manual work becomes tedious and inefficient. Automation saves from routine checks, but complete coverage requires well-thought-out strategies.

Problem:

Dynamic elements often change locators, DOM structure, classes, and styles at runtime.
Interacting via drag&drop, working with canvases, responsiveness on different devices, and animation is difficult to emulate with automated tests.
Tests become flaky due to asynchronous behavior and rendering delays.

Solution:

Use specialized tools: Selenium, Cypress, Playwright for flexible UI work, and for "visual" testing - Percy, Applitools.
Apply Page Object Model to separate logic and locators, and use dynamic waits (waits, retries).

For complex interactive elements - interact via low-level browser APIs (for example, through JS scripts or WebDriver Actions):

# Drag & Drop using Selenium WebDriver
from selenium.webdriver import ActionChains
action = ActionChains(driver)
action.click_and_hold(source).move_to_element(target).release().perform()

Key features:

The necessity of stable and unique locators.
Use of visual tests to detect "drift" in the UI.
Asynchronous waits (explicit waits, custom waits) to combat flakiness.

Tricky Questions.

Is it enough to test the UI only by "clicking" on elements (clicks and input)?

No. It is necessary to check hidden states, tooltips, rendering at different resolutions, and even the presence of animations or layout errors.

Can only Xpath be used to find all elements?

No. Xpath is not always readable, can be slow, and may break when the structure changes. Use CSS selectors, data-test-id, automationId - they are more stable.

Do visual automated tests guarantee that components are functional?

No. Visual tests catch UI bugs but do not check business logic, clickability, and correct interaction.

Common Mistakes and Anti-Patterns

Copy-pasting locators without reusing and abstracting.
Using too "broad" (non-unique) or unstable locators.
Ignoring the specifics of asynchronous loading and delays.
Running "flaky" UI tests in CI without mocks/fixtures for data.

Real-Life Example

Negative Case

Automated a complex multi-level table using Selenium exclusively through Xpath. Every release broke the locators, causing automated tests to fail massively. No visual tests were present, layout errors were not caught.

Pros:

Quick start, tests worked until the first serious refactoring.

Cons:

Support was impossible, high cost of changes, low return, missing significant bugs.

Positive Case

For testing a drag-and-drop component, we used Playwright and mocked events in the browser. For visual validation - Percy. UI layers were covered with the Page Object pattern.