Add additional test for IObservable compiled bindings.

tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/CompiledBindingExtensionTests.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Reactive.Subjects;
 using System.Text;
 using System.Threading.Tasks;
 using Avalonia.Controls;
@@ -41,7 +42,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
         }
 
         [Fact]
-        public void ResolvesStreamBindingCorrectly()
+        public void ResolvesStreamTaskBindingCorrectly()
         {
             using (UnitTestApplication.Start(TestServices.StyledWindow))
             {
@@ -68,6 +69,38 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
                 Assert.Equal(dataContext.TaskProperty.Result, textBlock.Text);
             }
         }
+
+        [Fact]
+        public void ResolvesStreamObservableBindingCorrectly()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+        xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.MarkupExtensions;assembly=Avalonia.Markup.Xaml.UnitTests'
+        x:DataContextType='{x:Type local:TestDataContext}'>
+    <TextBlock Text='{CompiledBinding ObservableProperty^}' Name='textBlock' />
+</Window>";
+                var loader = new AvaloniaXamlLoader();
+                var window = (Window)loader.Load(xaml);
+                var textBlock = window.FindControl<TextBlock>("textBlock");
+
+                DelayedBinding.ApplyBindings(textBlock);
+
+                var subject = new Subject<string>();
+                var dataContext = new TestDataContext
+                {
+                    ObservableProperty = subject
+                };
+
+                window.DataContext = dataContext;
+
+                subject.OnNext("foobar");
+
+                Assert.Equal("foobar", textBlock.Text);
+            }
+        }
     }
 
     public class TestDataContext
@@ -75,5 +108,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
         public string StringProperty { get; set; }
 
         public Task<string> TaskProperty { get; set; }
+
+        public IObservable<string> ObservableProperty { get; set; }
     }
 }