test: add a manual test

src/SamplesApp/UITests.Shared/UITests.Shared.projitems

@@ -2474,6 +2474,10 @@
       <SubType>Designer</SubType>
       <Generator>MSBuild:Compile</Generator>
     </Page>
+    <Page Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Controls\ScrollViewerTests\ScrollViewer_IsIntermediate.xaml">
+      <SubType>Designer</SubType>
+      <Generator>MSBuild:Compile</Generator>
+    </Page>
     <Page Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Controls\ScrollViewerTests\ScrollViewer_Content_Smaller_Than_Viewport.xaml">
       <SubType>Designer</SubType>
       <Generator>MSBuild:Compile</Generator>
@@ -9552,6 +9556,9 @@
     <Compile Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Controls\ScrollViewerTests\ScrollViewer_Simple.xaml.cs">
       <DependentUpon>ScrollViewer_Simple.xaml</DependentUpon>
     </Compile>
+    <Compile Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Controls\ScrollViewerTests\ScrollViewer_IsIntermediate.xaml.cs">
+      <DependentUpon>ScrollViewer_IsIntermediate.xaml</DependentUpon>
+    </Compile>
     <Compile Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Controls\ScrollViewerTests\ScrollViewer_Content_Smaller_Than_Viewport.xaml.cs">
       <DependentUpon>ScrollViewer_Content_Smaller_Than_Viewport.xaml</DependentUpon>
     </Compile>

src/SamplesApp/UITests.Shared/Windows_UI_Xaml_Controls/ScrollViewerTests/ScrollViewer_IsIntermediate.xaml

@@ -0,0 +1,25 @@
+<Page x:Class="UITests.Windows_UI_Xaml_Controls.ScrollViewerTests.ScrollViewer_IsIntermediate"
+	  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+	  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+	  xmlns:local="using:UITests.Windows_UI_Xaml_Controls.ScrollViewerTests"
+	  xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+	  xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+	  mc:Ignorable="d"
+	  Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
+
+	<StackPanel>
+		<TextBlock>
+			Repro steps:
+			<LineBreak />
+			1. Scroll the ScrollViewer below using the scroll bar. You should see the status below possibly change to "Last ScrollViewerViewChangedEventArgs.IsIntermediate = true" but then it must end up on "Last ScrollViewerViewChangedEventArgs.IsIntermediate = false"
+			<LineBreak />
+			2. Scroll the ScrollViewer below using the mouse wheel. You should see the status below possibly change to "Last ScrollViewerViewChangedEventArgs.IsIntermediate = true" but then it must end up on "Last ScrollViewerViewChangedEventArgs.IsIntermediate = false"
+		</TextBlock>
+		<ScrollViewer Height="400" Width="400" ViewChanged="ScrollViewer_ViewChanged">
+			<Border Height="800" Width="800" Background="LightBlue" BorderBrush="Black" BorderThickness="2">
+				<TextBlock Text="Scroll me" />
+			</Border>
+		</ScrollViewer>
+		<TextBlock x:Name="statusTb" Text="Last ScrollViewerViewChangedEventArgs.IsIntermediate = N/A" />
+	</StackPanel>
+</Page>

src/SamplesApp/UITests.Shared/Windows_UI_Xaml_Controls/ScrollViewerTests/ScrollViewer_IsIntermediate.xaml.cs

@@ -0,0 +1,19 @@
+using Microsoft.UI.Xaml.Controls;
+using Uno.UI.Samples.Controls;
+
+namespace UITests.Windows_UI_Xaml_Controls.ScrollViewerTests
+{
+	[Sample("Scrolling", IsManualTest = true)]
+	public sealed partial class ScrollViewer_IsIntermediate : Page
+	{
+		public ScrollViewer_IsIntermediate()
+		{
+			this.InitializeComponent();
+		}
+
+		private void ScrollViewer_ViewChanged(object sender, ScrollViewerViewChangedEventArgs e)
+		{
+			statusTb.Text = $"Last ScrollViewerViewChangedEventArgs.IsIntermediate = {e.IsIntermediate}";
+		}
+	}
+}