Added more GC.KeepAlive statements.

tests/Avalonia.Markup.UnitTests/Data/ExpressionObserverTests_Lifetime.cs

@@ -90,7 +90,8 @@ namespace Avalonia.Markup.UnitTests.Data
         {
             var scheduler = new TestScheduler();
             var update = scheduler.CreateColdObservable<Unit>();
-            var target = new ExpressionObserver(() => new { Foo = "foo" }, "Foo", update);
+            var data = new { Foo = "foo" };
+            var target = new ExpressionObserver(() => data, "Foo", update);
             var result = new List<object>();
 
             using (target.Subscribe(x => result.Add(x)))
@@ -101,6 +102,8 @@ namespace Avalonia.Markup.UnitTests.Data
 
             Assert.Equal(new[] { "foo" }, result);
             Assert.All(update.Subscriptions, x => Assert.NotEqual(Subscription.Infinite, x.Unsubscribe));
+
+            GC.KeepAlive(data);
         }
 
         private Recorded<Notification<object>> OnNext(long time, object value)

tests/Avalonia.Markup.UnitTests/Data/ExpressionObserverTests_Negation.cs

@@ -20,6 +20,8 @@ namespace Avalonia.Markup.UnitTests.Data
             var result = await target.Take(1);
 
             Assert.Equal(false, result);
+
+            GC.KeepAlive(data);
         }
 
         [Fact]
@@ -30,6 +32,8 @@ namespace Avalonia.Markup.UnitTests.Data
             var result = await target.Take(1);
 
             Assert.Equal(true, result);
+
+            GC.KeepAlive(data);
         }
 
         [Fact]
@@ -40,6 +44,8 @@ namespace Avalonia.Markup.UnitTests.Data
             var result = await target.Take(1);
 
             Assert.Equal(false, result);
+
+            GC.KeepAlive(data);
         }
 
         [Fact]
@@ -50,6 +56,8 @@ namespace Avalonia.Markup.UnitTests.Data
             var result = await target.Take(1);
 
             Assert.Equal(true, result);
+
+            GC.KeepAlive(data);
         }
 
         [Fact]
@@ -60,6 +68,8 @@ namespace Avalonia.Markup.UnitTests.Data
             var result = await target.Take(1);
 
             Assert.Equal(false, result);
+
+            GC.KeepAlive(data);
         }
 
         [Fact]
@@ -74,6 +84,8 @@ namespace Avalonia.Markup.UnitTests.Data
                     new InvalidCastException($"Unable to convert 'foo' to bool."),
                     BindingErrorType.Error), 
                 result);
+
+            GC.KeepAlive(data);
         }
 
         [Fact]
@@ -88,6 +100,8 @@ namespace Avalonia.Markup.UnitTests.Data
                     new InvalidCastException($"Unable to convert 'System.Object' to bool."),
                     BindingErrorType.Error),
                 result);
+
+            GC.KeepAlive(data);
         }
 
         [Fact]
@@ -97,6 +111,8 @@ namespace Avalonia.Markup.UnitTests.Data
             var target = new ExpressionObserver(data, "!Foo");
 
             Assert.False(target.SetValue("bar"));
+
+            GC.KeepAlive(data);
         }
     }
 }

tests/Avalonia.Markup.UnitTests/Data/Plugins/ExceptionValidationPluginTests.cs

@@ -35,6 +35,8 @@ namespace Avalonia.Markup.UnitTests.Data.Plugins
                 new BindingNotification(new ArgumentOutOfRangeException("value"), BindingErrorType.DataValidationError),
                 new BindingNotification(6),
             }, result);
+
+            GC.KeepAlive(data);
         }
 
         public class Data : NotifyingBase