Convert tests to UIThreadTestMethod pattern (#764)

* Convert ShouldConfigureGridSplitterAutomationPeer test to UIThreadTestMethod

- Changed [TestMethod] to [UIThreadTestMethod]
- Removed EnqueueAsync wrapper
- Added CompositionTargetHelper.ExecuteAfterCompositionRenderingAsync() after gridSplitter.Name assignment
- Added CompositionTargetHelper.ExecuteAfterCompositionRenderingAsync() after gridSplitter.SetValue call
- Added using CommunityToolkit.WinUI.Helpers for CompositionTargetHelper

Co-authored-by: michael-hawker <24302614+michael-hawker@users.noreply.github.com>

* Remove using

* Convert ComplexAsyncLoadUIExampleTest to UIThreadTestMethod

- Changed [TestMethod] to [UIThreadTestMethod]
- Removed EnqueueAsync wrapper
- Added CompositionTargetHelper.ExecuteAfterCompositionRenderingAsync() after LoadTestContentAsync
- Added CompositionTargetHelper.ExecuteAfterCompositionRenderingAsync() after UnloadTestContentAsync
- Added using CommunityToolkit.WinUI.Helpers for CompositionTargetHelper

Co-authored-by: michael-hawker <24302614+michael-hawker@users.noreply.github.com>

* Remove unnecessary using statement from ColorPicker test

The using CommunityToolkit.WinUI.Helpers is not needed as CompositionTargetHelper is already available through the test base class.

Co-authored-by: michael-hawker <24302614+michael-hawker@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: michael-hawker <24302614+michael-hawker@users.noreply.github.com>

Author: Copilot

components/ColorPicker/tests/ExampleColorPickerTestClass.cs

@@ -97,23 +97,22 @@ await EnqueueAsync(() =>
 
     // If you want to load other content not within a XAML page using the UIThreadTestMethod above.
     // Then you can do that using the Load/UnloadTestContentAsync methods.
-    [TestMethod]
+    [UIThreadTestMethod]
     public async Task ComplexAsyncLoadUIExampleTest()
     {
-        await EnqueueAsync(async () =>
-        {
-            var component = new ColorPicker();
-            Assert.IsNotNull(component);
-            Assert.IsFalse(component.IsLoaded);
+        var component = new ColorPicker();
+        Assert.IsNotNull(component);
+        Assert.IsFalse(component.IsLoaded);
 
-            await LoadTestContentAsync(component);
+        await LoadTestContentAsync(component);
+        await CompositionTargetHelper.ExecuteAfterCompositionRenderingAsync(() => { });
 
-            Assert.IsTrue(component.IsLoaded);
+        Assert.IsTrue(component.IsLoaded);
 
-            await UnloadTestContentAsync(component);
+        await UnloadTestContentAsync(component);
+        await CompositionTargetHelper.ExecuteAfterCompositionRenderingAsync(() => { });
 
-            Assert.IsFalse(component.IsLoaded);
-        });
+        Assert.IsFalse(component.IsLoaded);
     }
 
     // You can still use the UIThreadTestMethod to remove the extra layer for the dispatcher as well:

components/Sizers/tests/ExampleSizerBaseTestClass.cs

@@ -12,25 +12,24 @@ namespace SizersTests;
 [TestClass]
 public partial class ExampleSizerBaseTestClass : VisualUITestBase
 {
-    [TestMethod]
+    [UIThreadTestMethod]
     public async Task ShouldConfigureGridSplitterAutomationPeer()
     {
-        await EnqueueAsync(() =>
-        {
-            const string automationName = "MyCustomAutomationName";
-            const string name = "Sizer";
+        const string automationName = "MyCustomAutomationName";
+        const string name = "Sizer";
 
-            var gridSplitter = new GridSplitter();
-            var gridSplitterAutomationPeer = FrameworkElementAutomationPeer.CreatePeerForElement(gridSplitter) as SizerAutomationPeer;
+        var gridSplitter = new GridSplitter();
+        var gridSplitterAutomationPeer = FrameworkElementAutomationPeer.CreatePeerForElement(gridSplitter) as SizerAutomationPeer;
 
-            Assert.IsNotNull(gridSplitterAutomationPeer, "Verify that the AutomationPeer is SizerAutomationPeer.");
+        Assert.IsNotNull(gridSplitterAutomationPeer, "Verify that the AutomationPeer is SizerAutomationPeer.");
 
-            gridSplitter.Name = name;
-            Assert.IsTrue(gridSplitterAutomationPeer.GetName().Contains(name), "Verify that the UIA name contains the given Name of the GridSplitter (Sizer).");
+        gridSplitter.Name = name;
+        await CompositionTargetHelper.ExecuteAfterCompositionRenderingAsync(() => { });
+        Assert.IsTrue(gridSplitterAutomationPeer.GetName().Contains(name), "Verify that the UIA name contains the given Name of the GridSplitter (Sizer).");
 
-            gridSplitter.SetValue(AutomationProperties.NameProperty, automationName);
-            Assert.IsTrue(gridSplitterAutomationPeer.GetName().Contains(automationName), "Verify that the UIA name contains the customized AutomationProperties.Name of the GridSplitter.");
-        });
+        gridSplitter.SetValue(AutomationProperties.NameProperty, automationName);
+        await CompositionTargetHelper.ExecuteAfterCompositionRenderingAsync(() => { });
+        Assert.IsTrue(gridSplitterAutomationPeer.GetName().Contains(automationName), "Verify that the UIA name contains the customized AutomationProperties.Name of the GridSplitter.");
     }
 
     [UIThreadTestMethod]