Windows UI Automation

Detailed explanation

Windows UI Automation (UIA) is an accessibility framework introduced by Microsoft as part of the .NET Framework 3.0. It provides a programmatic way to access and manipulate UI elements in Windows applications. UIA is crucial for automated testing because it allows test automation tools to "see" and interact with the application's user interface in a consistent and reliable manner, regardless of the underlying technology used to build the application (e.g., WinForms, WPF, Win32).

UIA works by exposing a tree-like structure of UI elements, called the UI Automation tree. Each element in the tree is represented by an AutomationElement object, which provides properties and methods for accessing information about the element (e.g., its name, type, position, state) and for performing actions on it (e.g., clicking, typing, selecting).

Key Concepts:

• AutomationElement: Represents a UI element in the UI Automation tree. It's the fundamental building block for interacting with the UI.
• Automation Properties: Attributes of an AutomationElement that describe its characteristics, such as Name, ControlType, IsEnabled, IsOffscreen, and AutomationId.
• Control Patterns: Interfaces that expose specific functionality of a UI element, such as clicking a button (InvokePattern), setting a value in a text box (ValuePattern), or selecting an item in a list (SelectionPattern).
• Events: Notifications that are raised when the state of a UI element changes, such as when a button is clicked or a window is opened.

Practical Implementation:

To use UIA in your test automation code, you'll typically use a UIA client library. Several libraries are available, including:

• Microsoft UI Automation: The native .NET API for UIA. It provides the most direct access to the UIA framework but can be more complex to use.
• TestStack.White: An open-source framework built on top of UIA that simplifies UI automation. It provides a higher-level API that is easier to use and understand.
• FlaUI: Another open-source framework that offers a fluent API for UI automation. It supports multiple UI technologies, including WinForms, WPF, and UWP.

Here's a simple example using TestStack.White to launch a Notepad application and type some text:

using TestStack.White;
using TestStack.White.UIItems.WindowItems;
using TestStack.White.UIItems.TextBox;
using TestStack.White.Factory;
 
// Launch the Notepad application
Application application = Application.Launch("notepad.exe");
 
// Get the main window
Window window = application.GetWindow("Untitled - Notepad");
 
// Find the text box
TextBox textBox = window.Get<TextBox>(""); // Empty string gets the main textbox
 
// Type some text
textBox.Enter("Hello, UI Automation!");
 
// Close the application
application.Close();

This example demonstrates the basic steps involved in UI automation: launching the application, finding the target window, locating the UI element you want to interact with, and performing an action on that element.

Best Practices:

• Use AutomationId: Whenever possible, use the AutomationId property to identify UI elements. AutomationId is a unique identifier assigned to a UI element by the developer, and it's the most reliable way to locate elements in your test automation code. If AutomationId is not available, use other properties like Name or ControlType, but be aware that these properties may be less reliable and may change over time.
• Handle Dynamic UI: Many applications have dynamic UIs, where elements are added, removed, or changed based on user actions or application state. Use techniques like waiting for elements to appear or disappear before interacting with them. TestStack.White and FlaUI provide built-in support for waiting for elements.
• Implement Robust Error Handling: UI automation can be fragile, as it depends on the application's UI remaining consistent. Implement robust error handling to catch exceptions and retry operations if necessary. Log errors and provide informative messages to help diagnose problems.
• Use Page Object Model: The Page Object Model (POM) is a design pattern that helps to organize your UI automation code. In POM, each page or screen in your application is represented by a class, and the class contains methods for interacting with the elements on that page. This makes your code more modular, reusable, and maintainable.
• Consider Accessibility: When designing your UI automation tests, keep accessibility in mind. UIA is designed to be used by assistive technologies, so if your tests are accessible, they are more likely to be robust and reliable.
• Avoid Hardcoded Waits: Using Thread.Sleep() is generally discouraged. Instead, use explicit waits provided by the automation framework. These waits check for a specific condition (e.g., an element becoming visible) before proceeding, making your tests more reliable and efficient.

Common Tools:

• Inspect.exe: A tool provided by Microsoft that allows you to inspect the UI Automation tree of an application. It shows the properties and control patterns of each UI element, which is helpful for identifying elements and understanding how to interact with them. It's typically located in the Windows SDK.
• UI Spy: Another tool for inspecting the UI Automation tree. It offers similar functionality to Inspect.exe.
• Accessibility Insights: A tool from Microsoft that helps you identify accessibility issues in your application. It can also be used to inspect the UI Automation tree.

Example of using explicit waits with FlaUI:

using FlaUI.UIA3;
using FlaUI.Core.AutomationElements;
using FlaUI.Core.Conditions;
using System;
 
// Assuming you have launched your application and have a window object
// var window = app.GetMainWindow(automation);
 
// Get the automation object
var automation = new UIA3Automation();
 
// Example: Wait for a button to become enabled
ConditionFactory cf = new ConditionFactory(automation);
Condition isEnabledCondition = cf.ByIsEnabled(true);
 
// Find the button
Button myButton = window.FindFirstDescendant(cf.ByAutomationId("MyButton")).AsButton();
 
// Wait for the button to be enabled, with a timeout of 5 seconds
try
{
    myButton.WaitUntilEnabled(TimeSpan.FromSeconds(5));
    Console.WriteLine("Button is enabled!");
    myButton.Click();
}
catch (Exception ex)
{
    Console.WriteLine($"Button did not become enabled within the timeout: {ex.Message}");
}

This example demonstrates how to use WaitUntilEnabled to wait for a button to become enabled before clicking it. This makes the test more robust, as it avoids trying to click the button before it is ready.

By understanding the key concepts of Windows UI Automation and following best practices, you can create robust and reliable UI automation tests that help ensure the quality of your Windows applications.

Further reading

• Microsoft UI Automation Documentation
• TestStack.White
• FlaUI
• Accessibility Insights