Unit tests for ReactiveWindow and ReactiveUserControl

tests/Avalonia.ReactiveUI.UnitTests/ReactiveUserControlTest.cs

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+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using Avalonia.Controls;
+using Avalonia.UnitTests;
+using ReactiveUI;
+using Splat;
+using Xunit;
+
+namespace Avalonia.ReactiveUI.UnitTests
+{
+    public class ReactiveUserControlTest
+    {
+        public class ExampleViewModel : ReactiveObject { }
+
+        public class ExampleView : ReactiveUserControl<ExampleViewModel> { }
+
+        [Fact]
+        public void Data_Context_Should_Stay_In_Sync_With_Reactive_User_Control_View_Model() 
+        {
+            var view = new ExampleView();
+            var viewModel = new ExampleViewModel();
+            Assert.Null(view.ViewModel);
+
+            view.DataContext = viewModel;
+            Assert.Equal(view.ViewModel, viewModel);
+            Assert.Equal(view.DataContext, viewModel);
+
+            view.DataContext = null;
+            Assert.Null(view.ViewModel);
+            Assert.Null(view.DataContext);
+        }
+    }
+}

tests/Avalonia.ReactiveUI.UnitTests/ReactiveWindowTest.cs

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+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using Avalonia.Controls;
+using Avalonia.UnitTests;
+using ReactiveUI;
+using Splat;
+using Xunit;
+
+namespace Avalonia.ReactiveUI.UnitTests
+{
+    public class ReactiveWindowTest
+    {
+        public class ExampleViewModel : ReactiveObject { }
+
+        public class ExampleWindow : ReactiveWindow<ExampleViewModel> { }
+
+        [Fact]
+        public void Data_Context_Should_Stay_In_Sync_With_Reactive_Window_View_Model() 
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var view = new ExampleWindow();
+                var viewModel = new ExampleViewModel();
+                Assert.Null(view.ViewModel);
+
+                view.DataContext = viewModel;
+                Assert.Equal(view.ViewModel, viewModel);
+                Assert.Equal(view.DataContext, viewModel);
+
+                view.DataContext = null;
+                Assert.Null(view.ViewModel);
+                Assert.Null(view.DataContext);
+            }
+        }
+    }
+}