What is the 'element not found' error in UI automation tests? Where to look for the problem?

The "element not found" error in UI automation tests means that the test script was unable to find the element on the page it was trying to access (for example, a button, input field, or link). This can be caused by several reasons:

• The element truly does not exist on the page (for example, due to a bug in the application or an incorrect state).
• The element appears with a delay, and the test tries to find it too early (you need to add a wait).
• Incorrect locator (selector) used to find the element.
• The page did not fully load or a transition to another page occurred.

Where to look for the problem:

1. Check the correctness of the locator used in the test.
2. Ensure that the page is in the correct state and the element should be visible.
3. Add explicit waits before searching for the element.
4. Look at logs and screenshots, if available, to understand the UI state at the moment of the error.
5. Check if the UI or selectors have changed after the application update.