Added failing tests for brush invalidation.

tests/Avalonia.Controls.UnitTests/BorderTests.cs

@@ -1,6 +1,10 @@
 // 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.Media;
+using Avalonia.Rendering;
+using Avalonia.UnitTests;
+using Moq;
 using Xunit;
 
 namespace Avalonia.Controls.UnitTests
@@ -42,5 +46,22 @@ namespace Avalonia.Controls.UnitTests
 
             Assert.Equal(new Rect(6, 6, 0, 0), content.Bounds);
         }
+
+        [Fact]
+        public void Changing_Background_Brush_Color_Should_Invalidate_Visual()
+        {
+            var target = new Border()
+            {
+                Background = new SolidColorBrush(Colors.Red),
+            };
+
+            var root = new TestRoot(target);
+            var renderer = Mock.Get(root.Renderer);
+            renderer.ResetCalls();
+
+            ((SolidColorBrush)target.Background).Color = Colors.Green;
+
+            renderer.Verify(x => x.AddDirty(target), Times.Once);
+        }
     }
 }

tests/Avalonia.Controls.UnitTests/PanelTests.cs

@@ -3,7 +3,11 @@
 
 using System.Linq;
 using Avalonia.LogicalTree;
+using Avalonia.Media;
+using Avalonia.Rendering;
+using Avalonia.UnitTests;
 using Avalonia.VisualTree;
+using Moq;
 using Xunit;
 
 namespace Avalonia.Controls.UnitTests
@@ -115,5 +119,22 @@ namespace Avalonia.Controls.UnitTests
             Assert.Equal(new[] { child2, child1 }, panel.GetLogicalChildren());
             Assert.Equal(new[] { child2, child1 }, panel.GetVisualChildren());
         }
+
+        [Fact]
+        public void Changing_Background_Brush_Color_Should_Invalidate_Visual()
+        {
+            var target = new Panel()
+            {
+                Background = new SolidColorBrush(Colors.Red),
+            };
+
+            var root = new TestRoot(target);
+            var renderer = Mock.Get(root.Renderer);
+            renderer.ResetCalls();
+
+            ((SolidColorBrush)target.Background).Color = Colors.Green;
+
+            renderer.Verify(x => x.AddDirty(target), Times.Once);
+        }
     }
 }

tests/Avalonia.Controls.UnitTests/Presenters/ContentPresenterTests_Standalone.cs

@@ -13,6 +13,7 @@ using System;
 using System.Linq;
 using Xunit;
 using Avalonia.Rendering;
+using Avalonia.Media;
 
 namespace Avalonia.Controls.UnitTests.Presenters
 {
@@ -203,5 +204,22 @@ namespace Avalonia.Controls.UnitTests.Presenters
             Assert.NotEqual(foo, logicalChildren.First());
         }
 
+
+        [Fact]
+        public void Changing_Background_Brush_Color_Should_Invalidate_Visual()
+        {
+            var target = new ContentPresenter()
+            {
+                Background = new SolidColorBrush(Colors.Red),
+            };
+
+            var root = new TestRoot(target);
+            var renderer = Mock.Get(root.Renderer);
+            renderer.ResetCalls();
+
+            ((SolidColorBrush)target.Background).Color = Colors.Green;
+
+            renderer.Verify(x => x.AddDirty(target), Times.Once);
+        }
     }
-}
+}

tests/Avalonia.Controls.UnitTests/Shapes/RectangleTests.cs

@@ -0,0 +1,48 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Avalonia.Controls.Shapes;
+using Avalonia.Media;
+using Avalonia.UnitTests;
+using Moq;
+using Xunit;
+
+namespace Avalonia.Controls.UnitTests.Shapes
+{
+    public class RectangleTests
+    {
+        [Fact]
+        public void Changing_Fill_Brush_Color_Should_Invalidate_Visual()
+        {
+            var target = new Rectangle()
+            {
+                Fill = new SolidColorBrush(Colors.Red),
+            };
+
+            var root = new TestRoot(target);
+            var renderer = Mock.Get(root.Renderer);
+            renderer.ResetCalls();
+
+            ((SolidColorBrush)target.Fill).Color = Colors.Green;
+
+            renderer.Verify(x => x.AddDirty(target), Times.Once);
+        }
+
+        [Fact]
+        public void Changing_Stroke_Brush_Color_Should_Invalidate_Visual()
+        {
+            var target = new Rectangle()
+            {
+                Stroke = new SolidColorBrush(Colors.Red),
+            };
+
+            var root = new TestRoot(target);
+            var renderer = Mock.Get(root.Renderer);
+            renderer.ResetCalls();
+
+            ((SolidColorBrush)target.Stroke).Color = Colors.Green;
+
+            renderer.Verify(x => x.AddDirty(target), Times.Once);
+        }
+    }
+}

tests/Avalonia.Controls.UnitTests/TextBlockTests.cs

@@ -2,6 +2,10 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using Avalonia.Data;
+using Avalonia.Media;
+using Avalonia.Rendering;
+using Avalonia.UnitTests;
+using Moq;
 using Xunit;
 
 namespace Avalonia.Controls.UnitTests
@@ -25,5 +29,39 @@ namespace Avalonia.Controls.UnitTests
                 "",
                 textBlock.Text);
         }
+
+        [Fact]
+        public void Changing_Background_Brush_Color_Should_Invalidate_Visual()
+        {
+            var target = new TextBlock()
+            {
+                Background = new SolidColorBrush(Colors.Red),
+            };
+
+            var root = new TestRoot(target);
+            var renderer = Mock.Get(root.Renderer);
+            renderer.ResetCalls();
+
+            ((SolidColorBrush)target.Background).Color = Colors.Green;
+
+            renderer.Verify(x => x.AddDirty(target), Times.Once);
+        }
+
+        [Fact]
+        public void Changing_Foreground_Brush_Color_Should_Invalidate_Visual()
+        {
+            var target = new TextBlock()
+            {
+                Foreground = new SolidColorBrush(Colors.Red),
+            };
+
+            var root = new TestRoot(target);
+            var renderer = Mock.Get(root.Renderer);
+            renderer.ResetCalls();
+
+            ((SolidColorBrush)target.Foreground).Color = Colors.Green;
+
+            renderer.Verify(x => x.AddDirty(target), Times.Once);
+        }
     }
 }

tests/Avalonia.UnitTests/TestRoot.cs

@@ -19,6 +19,13 @@ namespace Avalonia.UnitTests
 
         public TestRoot()
         {
+            Renderer = Mock.Of<IRenderer>();
+        }
+
+        public TestRoot(IControl child)
+            : this()
+        {
+            Child = child;
         }
 
         event EventHandler<NameScopeEventArgs> INameScope.Registered