Fix #20625: simplify compiled binding regression tests

Address review feedback to reduce test complexity in XamlIlTests.

This change removes per-test UserControl helper classes and command
scaffolding that were not required to validate the compiler behavior.
Tests now use inline XAML in each [Fact] and shared lightweight mock
types for root and item data.

The compiled binding scenarios are still covered, including root
fallback inference and named DataContext resolution with ItemTemplate
and nested namescopes, but with less boilerplate and better readability.

tests/Avalonia.Markup.Xaml.UnitTests/Xaml/XamlIlTests.cs

@@ -432,9 +432,14 @@ namespace Avalonia.Markup.Xaml.UnitTests
         {
             using (UnitTestApplication.Start(TestServices.StyledWindow))
             {
-                var parsed = new XamlIlCompiledBindingRootControl();
+                var parsed = (CompiledBindingRootMock)AvaloniaRuntimeXamlLoader.Parse(@"
-
+<UserControl x:Class='Avalonia.Markup.Xaml.UnitTests.CompiledBindingRootMock'
-                var textBlock = Assert.IsType<TextBlock>(parsed.Content);
+    xmlns='https://github.com/avaloniaui'
+    xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+    <TextBlock Text='{CompiledBinding Greeting}'/>
+</UserControl>");
+                parsed.DataContext = parsed;
+                var textBlock = (TextBlock)parsed.Content!;
                 Assert.Equal("Hello", textBlock.Text);
             }
         }
@@ -444,10 +449,19 @@ namespace Avalonia.Markup.Xaml.UnitTests
         {
             using (UnitTestApplication.Start(TestServices.StyledWindow))
             {
-                var parsed = new XamlIlCompiledBindingTemplateControl();
+                var parsed = (ListBox)AvaloniaRuntimeXamlLoader.Parse(@"
-
+<ListBox Name='ListBoxRoot' ItemsSource='{CompiledBinding Items}'
-                var listBox = Assert.IsType<ListBox>(parsed.Content);
+    xmlns='https://github.com/avaloniaui'
-                Assert.NotNull(listBox.ItemTemplate);
+    xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+    xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests;assembly=Avalonia.Markup.Xaml.UnitTests'
+    x:DataType='local:CompiledBindingRootMock'>
+    <ListBox.ItemTemplate>
+        <DataTemplate x:DataType='local:CompiledBindingItemMock'>
+            <TextBlock Text='{CompiledBinding #ListBoxRoot.DataContext.RootProperty}' />
+        </DataTemplate>
+    </ListBox.ItemTemplate>
+</ListBox>");
+                Assert.NotNull(parsed.ItemTemplate);
             }
         }
 
@@ -456,9 +470,14 @@ namespace Avalonia.Markup.Xaml.UnitTests
         {
             using (UnitTestApplication.Start(TestServices.StyledWindow))
             {
-                var parsed = new XamlIlCompiledBindingRootControlWithMismatchedDataContext();
+                var parsed = (CompiledBindingRootMock)AvaloniaRuntimeXamlLoader.Parse(@"
-
+<UserControl x:Class='Avalonia.Markup.Xaml.UnitTests.CompiledBindingRootMock'
-                var textBlock = Assert.IsType<TextBlock>(parsed.Content);
+    xmlns='https://github.com/avaloniaui'
+    xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+    <TextBlock Text='{CompiledBinding Greeting}'/>
+</UserControl>");
+                parsed.DataContext = new object();
+                var textBlock = (TextBlock)parsed.Content!;
                 Assert.Null(textBlock.Text);
             }
         }
@@ -468,10 +487,25 @@ namespace Avalonia.Markup.Xaml.UnitTests
         {
             using (UnitTestApplication.Start(TestServices.StyledWindow))
             {
-                var parsed = new XamlIlCompiledBindingNestedTemplateControl();
+                 var parsed = (ListBox)AvaloniaRuntimeXamlLoader.Parse(@"
-
+<ListBox Name='ListBoxRoot' ItemsSource='{CompiledBinding Items}'
-                var listBox = Assert.IsType<ListBox>(parsed.Content);
+    xmlns='https://github.com/avaloniaui'
-                Assert.NotNull(listBox.ItemTemplate);
+    xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+    xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests;assembly=Avalonia.Markup.Xaml.UnitTests'
+    x:DataType='local:CompiledBindingRootMock'>
+    <ListBox.ItemTemplate>
+        <DataTemplate x:DataType='local:CompiledBindingItemMock'>
+            <ListBox ItemsSource='{CompiledBinding InnerItems}'>
+                <ListBox.ItemTemplate>
+                    <DataTemplate x:DataType='local:CompiledBindingItemMock'>
+                        <TextBlock Text='{CompiledBinding #ListBoxRoot.DataContext.RootProperty}' />
+                    </DataTemplate>
+                </ListBox.ItemTemplate>
+            </ListBox>
+        </DataTemplate>
+    </ListBox.ItemTemplate>
+</ListBox>");
+                Assert.NotNull(parsed.ItemTemplate);
             }
         }
     }
@@ -605,134 +639,16 @@ namespace Avalonia.Markup.Xaml.UnitTests
         
     }
 
-    public class XamlIlCompiledBindingRootControl : UserControl
+    public class CompiledBindingRootMock : UserControl
-    {
-        public string Greeting => "Hello";
-
-        public XamlIlCompiledBindingRootControl()
-        {
-            DataContext = this;
-            AvaloniaRuntimeXamlLoader.Load(@"
-<UserControl x:Class='Avalonia.Markup.Xaml.UnitTests.XamlIlCompiledBindingRootControl'
-    xmlns='https://github.com/avaloniaui'
-    xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
->
-    <TextBlock Text='{CompiledBinding Greeting}'/>
-</UserControl>
-", typeof(XamlIlTests).Assembly, this);
-        }
-    }
-
-    public class XamlIlCompiledBindingRootControlWithMismatchedDataContext : UserControl
     {
         public string Greeting => "Hello";
-
+        public string RootProperty => "RootValue";
-        public XamlIlCompiledBindingRootControlWithMismatchedDataContext()
+        public IReadOnlyList<CompiledBindingItemMock> Items { get; } = [new() { Name = "Outer", InnerItems = [new() { Name = "Inner" }] }];
-        {
-            DataContext = new object();
-            AvaloniaRuntimeXamlLoader.Load(@"
-<UserControl x:Class='Avalonia.Markup.Xaml.UnitTests.XamlIlCompiledBindingRootControlWithMismatchedDataContext'
-    xmlns='https://github.com/avaloniaui'
-    xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
->
-    <TextBlock Text='{CompiledBinding Greeting}'/>
-</UserControl>
-", typeof(XamlIlTests).Assembly, this);
-        }
-    }
-
-    public class XamlIlCompiledBindingTemplateControl : UserControl
-    {
-        public IReadOnlyList<XamlIlCompiledBindingTemplateItem> Items { get; } =
-            [new XamlIlCompiledBindingTemplateItem { Name = "Item" }];
-
-        public ICommand ButtonCommand { get; } = new XamlIlCompiledBindingNoOpCommand();
-
-        public XamlIlCompiledBindingTemplateControl()
-        {
-            DataContext = this;
-            AvaloniaRuntimeXamlLoader.Load(@"
-<UserControl x:Class='Avalonia.Markup.Xaml.UnitTests.XamlIlCompiledBindingTemplateControl'
-    xmlns='https://github.com/avaloniaui'
-    xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
-    xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests;assembly=Avalonia.Markup.Xaml.UnitTests'
-    x:DataType='local:XamlIlCompiledBindingTemplateControl'
->
-    <ListBox Name='ListBoxRoot' ItemsSource='{CompiledBinding Items}'>
-        <ListBox.ItemTemplate>
-            <DataTemplate x:DataType='local:XamlIlCompiledBindingTemplateItem'>
-                <StackPanel>
-                    <TextBlock Text='{CompiledBinding Name}' />
-                    <Button Command='{CompiledBinding #ListBoxRoot.DataContext.ButtonCommand}'
-                                    CommandParameter='{CompiledBinding .}' />
-                </StackPanel>
-            </DataTemplate>
-        </ListBox.ItemTemplate>
-    </ListBox>
-</UserControl>
-", typeof(XamlIlTests).Assembly, this);
-        }
-    }
-
-    public class XamlIlCompiledBindingNestedTemplateControl : UserControl
-    {
-        public IReadOnlyList<XamlIlCompiledBindingOuterItem> Items { get; } =
-            [new XamlIlCompiledBindingOuterItem()];
-
-        public ICommand ButtonCommand { get; } = new XamlIlCompiledBindingNoOpCommand();
-
-        public XamlIlCompiledBindingNestedTemplateControl()
-        {
-            DataContext = this;
-            AvaloniaRuntimeXamlLoader.Load(@"
-<UserControl x:Class='Avalonia.Markup.Xaml.UnitTests.XamlIlCompiledBindingNestedTemplateControl'
-    xmlns='https://github.com/avaloniaui'
-    xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
-    xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests;assembly=Avalonia.Markup.Xaml.UnitTests'
-    x:DataType='local:XamlIlCompiledBindingNestedTemplateControl'
->
-    <ListBox Name='ListBoxRoot' ItemsSource='{CompiledBinding Items}'>
-        <ListBox.ItemTemplate>
-            <DataTemplate x:DataType='local:XamlIlCompiledBindingOuterItem'>
-                <ListBox ItemsSource='{CompiledBinding InnerItems}'>
-                    <ListBox.ItemTemplate>
-                        <DataTemplate x:DataType='local:XamlIlCompiledBindingTemplateItem'>
-                            <Button Command='{CompiledBinding #ListBoxRoot.DataContext.ButtonCommand}'
-                                    CommandParameter='{CompiledBinding .}' />
-                        </DataTemplate>
-                    </ListBox.ItemTemplate>
-                </ListBox>
-            </DataTemplate>
-        </ListBox.ItemTemplate>
-    </ListBox>
-</UserControl>
-", typeof(XamlIlTests).Assembly, this);
-        }
-    }
-
-    public class XamlIlCompiledBindingOuterItem
-    {
-        public IReadOnlyList<XamlIlCompiledBindingTemplateItem> InnerItems { get; } =
-            [new XamlIlCompiledBindingTemplateItem { Name = "Inner" }];
     }
 
-    public class XamlIlCompiledBindingTemplateItem
+    public class CompiledBindingItemMock
     {
         public string Name { get; set; } = string.Empty;
-    }
+        public IReadOnlyList<CompiledBindingItemMock> InnerItems { get; set; } = Array.Empty<CompiledBindingItemMock>();
-
-    public class XamlIlCompiledBindingNoOpCommand : ICommand
-    {
-        public event EventHandler? CanExecuteChanged
-        {
-            add { }
-            remove { }
-        }
-
-        public bool CanExecute(object? parameter) => true;
-
-        public void Execute(object? parameter)
-        {
-        }
     }
 }