[Testing] Migration of Compatibility.Core platform-specific unit tests into device tests - 7 (#28409)

* Enabled the Shell and ObservableItemsSource for device test

* Updated CollectionViewTests.Android.cs

* Addressed the feedback

* Removed three test cases from the CollectionView test

* Corrected the misspelled words

Author: nivetha-nagalingam

src/Controls/tests/DeviceTests/Elements/CollectionView/CollectionViewTests.Android.cs

@@ -5,6 +5,8 @@
 using Microsoft.Maui.Handlers;
 using Microsoft.Maui.Platform;
 using Xunit;
+using System.Collections.ObjectModel;
+using System.Linq;
 
 namespace Microsoft.Maui.DeviceTests
 {
@@ -86,6 +88,102 @@ await CreateHandlerAndAddToWindow<IWindowHandler>(contentPage,
 				});
 		}
 
+		//src/Compatibility/Core/tests/Android/RendererTests.cs
+		[Fact(DisplayName = "EmptySource should have a count of zero")]
+		[Trait("Category", "CollectionView")]
+		public void EmptySourceCountIsZero()
+		{
+			var emptySource = new EmptySource();
+			var count = emptySource.Count;
+			Assert.Equal(0, count);
+		}
+
+		//src/Compatibility/Core/tests/Android/ObservableItemsSourceTests.cs#L52
+		[Fact(DisplayName = "CollectionView with SnapPointsType set should not crash")]
+		public async Task SnapPointsDoNotCrashOnOlderAPIs()
+		{
+			SetupBuilder();
+
+			var collectionView = new CollectionView();
+
+			var itemsLayout = new LinearItemsLayout(ItemsLayoutOrientation.Vertical)
+			{
+				SnapPointsType = SnapPointsType.Mandatory
+			};
+			collectionView.ItemsLayout = itemsLayout;
+
+			await InvokeOnMainThreadAsync(() =>
+			{
+				var handler = CreateHandler<CollectionViewHandler>(collectionView);
+
+				var platformView = handler.PlatformView;
+
+				collectionView.Handler = null;
+			});
+		}
+
+		//src/Compatibility/Core/tests/Android/ObservableItemsSourceTests.cs#L52
+		[Fact(DisplayName = "ObservableCollection modifications are reflected after UI thread processes them")]
+		public async Task ObservableSourceItemsCountConsistent()
+		{
+			SetupBuilder();
+
+			var source = new ObservableCollection<string>();
+			source.Add("Item 1");
+			source.Add("Item 2");
+			var ois = ItemsSourceFactory.Create(source, Application.Current, new MockCollectionChangedNotifier());
+
+			Assert.Equal(2, ois.Count);
+
+			source.Add("Item 3");
+			var count = 0;
+			await InvokeOnMainThreadAsync(() =>
+			{ 
+				count = ois.Count;
+				Assert.Equal(3, ois.Count);
+			});
+		}
+
+		class MockCollectionChangedNotifier : ICollectionChangedNotifier
+		{
+			public int InsertCount;
+			public int RemoveCount;
+
+			public void NotifyDataSetChanged()
+			{
+			}
+
+			public void NotifyItemChanged(IItemsViewSource source, int startIndex)
+			{
+			}
+
+			public void NotifyItemInserted(IItemsViewSource source, int startIndex)
+			{
+				InsertCount += 1;
+			}
+
+			public void NotifyItemMoved(IItemsViewSource source, int fromPosition, int toPosition)
+			{
+			}
+
+			public void NotifyItemRangeChanged(IItemsViewSource source, int start, int end)
+			{
+			}
+
+			public void NotifyItemRangeInserted(IItemsViewSource source, int startIndex, int count)
+			{
+			}
+
+			public void NotifyItemRangeRemoved(IItemsViewSource source, int startIndex, int count)
+			{
+			}
+
+			public void NotifyItemRemoved(IItemsViewSource source, int startIndex)
+			{
+				RemoveCount += 1;
+			}
+		}
+
 		Rect GetCollectionViewCellBounds(IView cellContent)
 		{
 			if (!cellContent.ToPlatform().IsLoaded())

src/Controls/tests/DeviceTests/Elements/CollectionView/CollectionViewTests.iOS.cs

@@ -10,6 +10,8 @@
 using UIKit;
 using Xunit;
 using Xunit.Sdk;
+using Foundation;
+using Microsoft.Maui.Handlers;
 
 namespace Microsoft.Maui.DeviceTests
 {
@@ -125,6 +127,73 @@ await InvokeOnMainThreadAsync(() =>
 #endif
 		}
 
+		//src/Compatibility/Core/tests/iOS/ObservableItemsSourceTests.cs
+		[Fact(DisplayName = "IndexPath Range Generation Is Correct")]
+		public void GenerateIndexPathRange()
+		{
+			SetupBuilder();
+
+			var result = IndexPathHelpers.GenerateIndexPathRange(0, 0, 5);
+
+			Assert.Equal(5, result.Length);
+
+			Assert.Equal(0, result[0].Section);
+			Assert.Equal(0, (int)result[0].Item);
+
+			Assert.Equal(0, result[4].Section);
+			Assert.Equal(4, (int)result[4].Item);
+		}
+
+		//src/Compatibility/Core/tests/iOS/ObservableItemsSourceTests.cs
+		[Fact(DisplayName = "IndexPath Range Generation For Loops Is Correct")]
+		public void GenerateIndexPathRangeForLoop()
+		{
+			SetupBuilder();
+
+			var result = IndexPathHelpers.GenerateLoopedIndexPathRange(0, 15, 3, 2, 3);
+
+			Assert.Equal(9, result.Length);
+
+			for (int i = 0; i < result.Length; i++)
+			{
+				Assert.Equal(0, result[i].Section);
+			}
+
+			Assert.Equal(2, (int)result[0].Item);
+			Assert.Equal(3, (int)result[1].Item);
+			Assert.Equal(4, (int)result[2].Item);
+
+			Assert.Equal(7, (int)result[3].Item);
+			Assert.Equal(8, (int)result[4].Item);
+			Assert.Equal(9, (int)result[5].Item);
+
+			Assert.Equal(12, (int)result[6].Item);
+			Assert.Equal(13, (int)result[7].Item);
+			Assert.Equal(14, (int)result[8].Item);
+		}
+
+		//src/Compatibility/Core/tests/iOS/ObservableItemsSourceTests.cs
+		[Fact(DisplayName = "IndexPath Validity Check Is Correct")]
+		public void IndexPathValidTest()
+		{
+			var list = new List<string>
+			{
+				"one",
+				"two",
+				"three"
+			};
+
+			var source = new ListSource((IEnumerable<object>)list);
+
+			var valid = NSIndexPath.FromItemSection(2, 0);
+			var invalidItem = NSIndexPath.FromItemSection(7, 0);
+			var invalidSection = NSIndexPath.FromItemSection(1, 9);
+
+			Assert.True(source.IsIndexPathValid(valid));
+			Assert.False(source.IsIndexPathValid(invalidItem));
+			Assert.False(source.IsIndexPathValid(invalidSection));
+		}
+
 		/// <summary>
 		/// Simulates what a developer might do with a Page/View
 		/// </summary>

src/Controls/tests/DeviceTests/Elements/Shell/ShellTests.Android.cs

@@ -454,6 +454,68 @@ await CreateHandlerAndAddToWindow<ShellRenderer>(shell, async (handler) =>
 			});
 		}
 
+		//src/Compatibility/Core/tests/Android/ShellTests.cs
+		[Fact(DisplayName = "Flyout Header Changes When Updated")]
+		public async Task FlyoutHeaderReactsToChanges()
+		{
+			SetupBuilder();
+
+			var initialHeader = new Label() { Text = "Hello" };
+			var newHeader = new Label() { Text = "Hello Part 2" };
+
+			var shell = await CreateShellAsync(shell =>
+			{
+				shell.CurrentItem = new FlyoutItem() { Items = { new ContentPage() }, Title = "Flyout Item" };
+				shell.FlyoutHeader = initialHeader;
+			});
+
+			await CreateHandlerAndAddToWindow<ShellRenderer>(shell, async (handler) =>
+			{				
+				var initialHeaderPlatformView = initialHeader.ToPlatform();
+				Assert.NotNull(initialHeaderPlatformView);
+				Assert.NotNull(initialHeader.Handler);
+
+				shell.FlyoutHeader = newHeader;
+
+				var newHeaderPlatformView = newHeader.ToPlatform();
+				Assert.NotNull(newHeaderPlatformView);
+				Assert.NotNull(newHeader.Handler);
+
+				Assert.Null(initialHeader.Handler);
+
+				await OpenFlyout(handler);
+
+				var appBar = newHeaderPlatformView.GetParentOfType<AppBarLayout>();
+				Assert.NotNull(appBar);
+			});
+		}
+
+		//src/Compatibility/Core/tests/Android/ShellTests.cs
+		[Fact(DisplayName = "Ensure Default Colors are White for BottomNavigationView")]
+		public async Task ShellTabColorsDefaultToWhite()
+		{
+			SetupBuilder();
+
+			var shell = await CreateShellAsync(shell => 
+			{
+				shell.Items.Add(new Tab() { Items = { new ContentPage() }, Title = "Tab 1" });
+			});
+
+			await CreateHandlerAndAddToWindow<ShellRenderer>(shell, (handler) =>
+			{
+				var bottomNavigationView = GetDrawerLayout(handler).GetFirstChildOfType<BottomNavigationView>();
+				Assert.NotNull(bottomNavigationView);
+
+				var background = bottomNavigationView.Background;
+				Assert.NotNull(background);
+
+				if (background is ColorChangeRevealDrawable changeRevealDrawable)
+				{
+					Assert.Equal(Android.Graphics.Color.White, changeRevealDrawable.EndColor);
+				}
+			});
+		}
+
 		protected AView GetFlyoutPlatformView(ShellRenderer shellRenderer)
 		{
 			var drawerLayout = GetDrawerLayout(shellRenderer);