Add tests for property binding threading.

- Added a failing tests for styled property binding with threading
- Made direct property test actually confirm that binding was done on UI thread

tests/Avalonia.Base.UnitTests/Avalonia.Base.UnitTests.csproj

@@ -17,6 +17,9 @@
     <EmbeddedResource Remove="..\Avalonia.RenderTests\Assets\NotoColorEmoji.ttf" />
     <EmbeddedResource Include="Media\TextFormatting\BreakPairTable.txt" />
   </ItemGroup>
+  <ItemGroup>
+    <PackageReference Include="Nito.AsyncEx.Context" Version="5.1.2" />
+  </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\src\Avalonia.Base\Avalonia.Base.csproj" />
     <ProjectReference Include="..\..\src\Markup\Avalonia.Markup.Xaml.Loader\Avalonia.Markup.Xaml.Loader.csproj" />

tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Binding.cs

@@ -12,6 +12,7 @@ using Avalonia.Platform;
 using Avalonia.Threading;
 using Avalonia.UnitTests;
 using Moq;
+using Nito.AsyncEx;
 using Xunit;
 
 #nullable enable
@@ -920,6 +921,120 @@ namespace Avalonia.Base.UnitTests
             }
         }
 
+        [Theory]
+        [InlineData(BindingPriority.LocalValue)]
+        [InlineData(BindingPriority.Style)]
+        public void Typed_Bind_Executes_On_UIThread(BindingPriority priority)
+        {
+            AsyncContext.Run(async () =>
+            {
+                var target = new Class1();
+                var source = new Subject<string>();
+                var currentThreadId = Thread.CurrentThread.ManagedThreadId;
+                var raised = 0;
+
+                var threadingInterfaceMock = new Mock<IPlatformThreadingInterface>();
+                threadingInterfaceMock.SetupGet(mock => mock.CurrentThreadIsLoopThread)
+                    .Returns(() => Thread.CurrentThread.ManagedThreadId == currentThreadId);
+
+                var services = new TestServices(
+                    threadingInterface: threadingInterfaceMock.Object);
+
+                target.PropertyChanged += (s, e) =>
+                {
+                    Assert.Equal(currentThreadId, Thread.CurrentThread.ManagedThreadId);
+                    ++raised;
+                };
+
+                using (UnitTestApplication.Start(services))
+                {
+                    target.Bind(Class1.FooProperty, source, priority);
+
+                    await Task.Run(() => source.OnNext("foobar"));
+                    Dispatcher.UIThread.RunJobs();
+
+                    Assert.Equal("foobar", target.GetValue(Class1.FooProperty));
+                    Assert.Equal(1, raised);
+                }
+            });
+        }
+
+        [Theory]
+        [InlineData(BindingPriority.LocalValue)]
+        [InlineData(BindingPriority.Style)]
+        public void Untyped_Bind_Executes_On_UIThread(BindingPriority priority)
+        {
+            AsyncContext.Run(async () =>
+            {
+                var target = new Class1();
+                var source = new Subject<object>();
+                var currentThreadId = Thread.CurrentThread.ManagedThreadId;
+                var raised = 0;
+
+                var threadingInterfaceMock = new Mock<IPlatformThreadingInterface>();
+                threadingInterfaceMock.SetupGet(mock => mock.CurrentThreadIsLoopThread)
+                    .Returns(() => Thread.CurrentThread.ManagedThreadId == currentThreadId);
+
+                var services = new TestServices(
+                    threadingInterface: threadingInterfaceMock.Object);
+
+                target.PropertyChanged += (s, e) =>
+                {
+                    Assert.Equal(currentThreadId, Thread.CurrentThread.ManagedThreadId);
+                    ++raised;
+                };
+
+                using (UnitTestApplication.Start(services))
+                {
+                    target.Bind(Class1.FooProperty, source, priority);
+
+                    await Task.Run(() => source.OnNext("foobar"));
+                    Dispatcher.UIThread.RunJobs();
+
+                    Assert.Equal("foobar", target.GetValue(Class1.FooProperty));
+                    Assert.Equal(1, raised);
+                }
+            });
+        }
+
+        [Theory]
+        [InlineData(BindingPriority.LocalValue)]
+        [InlineData(BindingPriority.Style)]
+        public void BindingValue_Bind_Executes_On_UIThread(BindingPriority priority)
+        {
+            AsyncContext.Run(async () =>
+            {
+                var target = new Class1();
+                var source = new Subject<BindingValue<string>>();
+                var currentThreadId = Thread.CurrentThread.ManagedThreadId;
+                var raised = 0;
+
+                var threadingInterfaceMock = new Mock<IPlatformThreadingInterface>();
+                threadingInterfaceMock.SetupGet(mock => mock.CurrentThreadIsLoopThread)
+                    .Returns(() => Thread.CurrentThread.ManagedThreadId == currentThreadId);
+
+                var services = new TestServices(
+                    threadingInterface: threadingInterfaceMock.Object);
+
+                target.PropertyChanged += (s, e) =>
+                {
+                    Assert.Equal(currentThreadId, Thread.CurrentThread.ManagedThreadId);
+                    ++raised;
+                };
+
+                using (UnitTestApplication.Start(services))
+                {
+                    target.Bind(Class1.FooProperty, source, priority);
+
+                    await Task.Run(() => source.OnNext("foobar"));
+                    Dispatcher.UIThread.RunJobs();
+
+                    Assert.Equal("foobar", target.GetValue(Class1.FooProperty));
+                    Assert.Equal(1, raised);
+                }
+            });
+        }
+
         [Fact]
         public async Task Bind_With_Scheduler_Executes_On_Scheduler()
         {

tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Direct.cs

@@ -7,8 +7,10 @@ using System.Threading.Tasks;
 using Avalonia.Data;
 using Avalonia.Logging;
 using Avalonia.Platform;
+using Avalonia.Threading;
 using Avalonia.UnitTests;
 using Moq;
+using Nito.AsyncEx;
 using Xunit;
 
 namespace Avalonia.Base.UnitTests
@@ -519,25 +521,39 @@ namespace Avalonia.Base.UnitTests
         }
 
         [Fact]
-        public async Task Bind_Executes_On_UIThread()
+        public void Bind_Executes_On_UIThread()
         {
-            var target = new Class1();
-            var source = new Subject<object>();
-            var currentThreadId = Thread.CurrentThread.ManagedThreadId;
+            AsyncContext.Run(async () =>
+            {
+                var target = new Class1();
+                var source = new Subject<object>();
+                var currentThreadId = Thread.CurrentThread.ManagedThreadId;
+                var raised = 0;
 
-            var threadingInterfaceMock = new Mock<IPlatformThreadingInterface>();
-            threadingInterfaceMock.SetupGet(mock => mock.CurrentThreadIsLoopThread)
-                .Returns(() => Thread.CurrentThread.ManagedThreadId == currentThreadId);
+                var threadingInterfaceMock = new Mock<IPlatformThreadingInterface>();
+                threadingInterfaceMock.SetupGet(mock => mock.CurrentThreadIsLoopThread)
+                    .Returns(() => Thread.CurrentThread.ManagedThreadId == currentThreadId);
 
-            var services = new TestServices(
-                threadingInterface: threadingInterfaceMock.Object);
+                var services = new TestServices(
+                    threadingInterface: threadingInterfaceMock.Object);
 
-            using (UnitTestApplication.Start(services))
-            {
-                target.Bind(Class1.FooProperty, source);
+                target.PropertyChanged += (s, e) =>
+                {
+                    Assert.Equal(currentThreadId, Thread.CurrentThread.ManagedThreadId);
+                    ++raised;
+                };
 
-                await Task.Run(() => source.OnNext("foobar"));
-            }
+                using (UnitTestApplication.Start(services))
+                {
+                    target.Bind(Class1.FooProperty, source);
+
+                    await Task.Run(() => source.OnNext("foobar"));
+                    Dispatcher.UIThread.RunJobs();
+
+                    Assert.Equal("foobar", target.Foo);
+                    Assert.Equal(1, raised);
+                }
+            });
         }
 
         [Fact]