How can I see the XCUIElement tree in Appium?

In iOS UI testing using XCUITest framework, viewing the hierarchy of XCUIElements can be incredibly helpful for debugging and writing efficient UI tests. There are several ways to inspect the XCUIElement tree:

1. Using print function in Xcode

You can print the XCUIElement tree directly in your Xcode console. To do this, you simply add a debug line in your UI test case where you want to capture the UI hierarchy. Here’s an example:

swift
print(XCUIApplication().debugDescription)

This line of code will print the entire hierarchy of UI elements of the current application state to the Xcode console. This is particularly useful for understanding which elements are available on the screen at any point in your test.

2. Using Xcode’s View Hierarchy Debugger

While not directly showing XCUIElements, Xcode’s built-in View Hierarchy Debugger can be used during UI tests to visually inspect the UI elements. To use this:

• Run your app from Xcode and navigate to the screen you want to inspect.
• Pause the running app using the pause button in the debugger controls.
• Click on the Debug View Hierarchy button in the debug area (it looks like a 3D cube).

This will bring up a 3D visual representation of the UI layers. Although this shows UIViews rather than XCUIElements, it's still very useful for understanding the layout and view structure, which directly correlates to how you might access these elements using XCUITest.

3. Using Accessibility Inspector

The Accessibility Inspector provided by Apple is another tool that can be used for inspecting the UI element hierarchy. It’s part of the Xcode additional tools and can be used to inspect elements' accessibility labels, identifiers, and other properties, which are critical for XCUITests. Here’s how to use it:

• Open Accessibility Inspector from Xcode or directly from Spotlight.
• Connect it to your running app on Simulator or a real device.
• Use the inspection target tool (crosshair) to click on any element within your app to see its details.

This tool is particularly useful for checking that elements have the correct accessibility identifiers, which are often used to locate elements in XCUI tests.

Example Use Case

Imagine you are testing an app with a complex form containing multiple text fields, buttons, and labels. During testing, you encounter a failure trying to tap a submit button. By printing out the XCUIElement hierarchy using the print function or using the Accessibility Inspector, you might discover that the button is not visible due to a scrolling issue or it lacks a proper accessibility identifier needed for your test script to identify it.

Using these tools to view the XCUIElement tree helps streamline creating robust and reliable UI tests by providing a clear understanding of the app’s UI structure at runtime.