test: Verify fix for unoplatform#4899, unoplatform#4907

Author: MartinZikmund

src/Uno.UI.RuntimeTests/MUX/Microsoft_UI_Xaml_Controls/TabView/TabViewTests.Uno.cs

@@ -0,0 +1,50 @@
+using System.Collections.ObjectModel;
+using Microsoft.UI.Xaml.Controls;
+using Microsoft.UI.Xaml.Controls.Primitives;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using MUXControlsTestApp.Utilities;
+using Private.Infrastructure;
+
+namespace Windows.UI.Xaml.Tests.MUXControls.ApiTests
+{
+	public partial class TabViewTests
+	{
+#if HAS_UNO
+		[TestMethod]
+		public void VerifyItemsAreCreatedOnlyOnce()
+		{
+			TabView tabView = null;
+			RunOnUIThread.Execute(() =>
+			{
+				tabView = new TabView();
+				TestServices.WindowHelper.WindowContent = tabView;
+
+				var items = new ObservableCollection<int>()
+				{
+					1, 2, 3
+				};
+
+				int containerContentChangingCounter = 0;
+
+				var listView = tabView.GetTemplateChild<TabViewListView>("TabListView");
+				listView.ContainerContentChanging += (s, e) =>
+				{
+					if (e.ItemIndex == 0)
+					{
+						containerContentChangingCounter++;
+					}
+				};
+
+				tabView.TabItemsSource = items;
+
+				tabView.UpdateLayout();
+
+				TestServices.WindowHelper.WaitForIdle();
+
+				// Only one container should be generated for the first item.
+				Assert.AreEqual(1, containerContentChangingCounter);
+			});
+		}
+#endif
+	}
+}

src/Uno.UI.RuntimeTests/MUX/Microsoft_UI_Xaml_Controls/TabView/TabViewTests.cs

@@ -33,9 +33,8 @@ namespace Windows.UI.Xaml.Tests.MUXControls.ApiTests
 {
 
 	[TestClass]
-	public class TabViewTests
+	public partial class TabViewTests
 	{
-
 		[TestMethod]
 		[Ignore("Automation peers are not fully supported on Uno https://github.com/unoplatform/uno/issues/4558")]
 		public void VerifyCompactTabWidthVisualStates()