Testing Model

Split tests by what they need from Windows.

Test Layers

Layer	Tool	Runs where
Pure logic	MSTest, NUnit, or xUnit	Fast local Windows CI/dev shell
XAML runtime	WinUI Unit Test App, `[UITestMethod]`	Windows with WinUI test host
Native UI automation	Appium with Windows driver	Windows desktop session
Accessibility	Accessibility Insights for Windows	Windows desktop session
WebView2 web content	Playwright	Windows with WebView2 target
Package/release	WACK and Store validation	Windows machine and/or Partner Center

Keep Logic Out Of XAML

Move business logic into a core library:

MyApp.Core -> normal unit tests
MyApp -> WinUI app shell
MyApp.WinUITests -> XAML/UI-thread tests only

This keeps most tests fast and avoids requiring a XAML runtime for every assertion.

XAML Test Example

[TestClass]
public class WindowTests
{
    [UITestMethod]
    public void CreatesGrid()
    {
        var grid = new Microsoft.UI.Xaml.Controls.Grid();
        Assert.AreEqual(0, grid.MinWidth);
    }
}

Use [UITestMethod] when the test touches XAML objects that require a UI thread.

UI Automation

Use AutomationProperties.AutomationId on important controls so Appium and Accessibility Insights can find stable targets.

<Button
    Content="Save"
    AutomationProperties.AutomationId="SaveButton" />

Gotcha: A normal unit test project can test pure code, but it is the wrong host for XAML runtime behavior unless you follow the target framework, runtime identifier, and bootstrap guidance.