Fixed failing test.

And removed `TestServices.WindowImpl` as it was being ignored.

tests/Avalonia.Controls.UnitTests/WindowTests.cs

@@ -5,6 +5,7 @@
 // -----------------------------------------------------------------------
 
 using Avalonia.Platform;
+using Avalonia.UnitTests;
 using Moq;
 using Xunit;
 
@@ -15,11 +16,11 @@ namespace Avalonia.Controls.UnitTests
         [Fact]
         public void Setting_Title_Should_Set_Impl_Title()
         {
-            using (AvaloniaLocator.EnterScope())
-            {
-                var windowImpl = new Mock<IWindowImpl>();
-                AvaloniaLocator.CurrentMutable.Bind<IWindowImpl>().ToConstant(windowImpl.Object);
+            var windowImpl = new Mock<IWindowImpl>();
+            var windowingPlatform = new MockWindowingPlatform(() => windowImpl.Object);
 
+            using (UnitTestApplication.Start(new TestServices(windowingPlatform: windowingPlatform)))
+            {
                 var target = new Window();
 
                 target.Title = "Hello World";

tests/Avalonia.UnitTests/TestServices.cs

@@ -67,7 +67,6 @@ namespace Avalonia.UnitTests
             IStyler styler = null,
             Func<Styles> theme = null,
             IPlatformThreadingInterface threadingInterface = null,
-            IWindowImpl windowImpl = null,
             IWindowingPlatform windowingPlatform = null)
         {
             AssetLoader = assetLoader;
@@ -83,7 +82,6 @@ namespace Avalonia.UnitTests
             Styler = styler;
             Theme = theme;
             ThreadingInterface = threadingInterface;
-            WindowImpl = windowImpl;
             WindowingPlatform = windowingPlatform;
         }
 
@@ -100,7 +98,6 @@ namespace Avalonia.UnitTests
         public IStyler Styler { get; }
         public Func<Styles> Theme { get; }
         public IPlatformThreadingInterface ThreadingInterface { get; }
-        public IWindowImpl WindowImpl { get; }
         public IWindowingPlatform WindowingPlatform { get; }
 
         public TestServices With(
@@ -134,7 +131,6 @@ namespace Avalonia.UnitTests
                 styler: styler ?? Styler,
                 theme: theme ?? Theme,
                 threadingInterface: threadingInterface ?? ThreadingInterface,
-                windowImpl: windowImpl ?? WindowImpl,
                 windowingPlatform: windowingPlatform ?? WindowingPlatform);
         }