Demonstrate leak in test.

tests/Perspex.LeakTests/ControlTests.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using JetBrains.dotMemoryUnit;
+using Perspex.Collections;
 using Perspex.Controls;
 using Perspex.Controls.Primitives;
 using Perspex.Controls.Templates;
@@ -207,6 +208,40 @@ namespace Perspex.LeakTests
             }
         }
 
+        [Fact]
+        public void TextBox_Class_Listeners_Are_Freed()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                TextBox textBox;
+
+                var window = new Window
+                {
+                    Content = textBox = new TextBox()
+                };
+
+                // Do a layout and make sure that TextBox gets added to visual tree and its 
+                // template applied.
+                LayoutManager.Instance.ExecuteInitialLayoutPass(window);
+                Assert.Same(textBox, window.Presenter.Child);
+
+                // Get the border from the TextBox template.
+                var border = textBox.GetTemplateChildren().FirstOrDefault(x => x.Name == "border");
+
+                // The TextBox should have subscriptions to its Classes collection from the
+                // default theme.
+                Assert.NotEmpty(((InccDebug)textBox.Classes).GetCollectionChangedSubscribers());
+
+                // Clear the content and ensure the TextBox is removed.
+                window.Content = null;
+                LayoutManager.Instance.ExecuteLayoutPass();
+                Assert.Null(window.Presenter.Child);
+
+                // Check that the TextBox has no subscriptions to its Classes collection.
+                Assert.Null(((InccDebug)textBox.Classes).GetCollectionChangedSubscribers());
+            }
+        }
+
         [Fact]
         public void TreeView_Is_Freed()
         {

tests/Perspex.UnitTests/TestServices.cs

@@ -6,6 +6,7 @@ using System.Reflection;
 using Moq;
 using Perspex.Input;
 using Perspex.Layout;
+using Perspex.Markup.Xaml;
 using Perspex.Platform;
 using Perspex.Shared.PlatformSupport;
 using Perspex.Styling;
@@ -26,7 +27,7 @@ namespace Perspex.UnitTests
             renderInterface: s_fixture.Create<IPlatformRenderInterface>(),
             standardCursorFactory: Mock.Of<IStandardCursorFactory>(),
             styler: new Styler(),
-            theme: () => new DefaultTheme(),
+            theme: () => CreateDefaultTheme(),
             threadingInterface: Mock.Of<IPlatformThreadingInterface>(x => x.CurrentThreadIsLoopThread == true),
             windowingPlatform: new MockWindowingPlatform());
 
@@ -106,5 +107,20 @@ namespace Perspex.UnitTests
                 windowImpl: windowImpl ?? WindowImpl,
                 windowingPlatform: windowingPlatform ?? WindowingPlatform);
         }
+
+        private static Styles CreateDefaultTheme()
+        {
+            var result = new Styles
+            {
+                new DefaultTheme(),
+            };
+
+            var loader = new PerspexXamlLoader();
+            var baseLight = (IStyle)loader.Load(
+                new Uri("resm:Perspex.Themes.Default.Accents.BaseLight.paml?assembly=Perspex.Themes.Default"));
+            result.Add(baseLight);
+
+            return result;
+        }
     }
 }