Add render tests for BackgroundSizing parity

tests/Avalonia.RenderTests/Controls/BorderTests.cs

@@ -109,6 +109,30 @@ namespace Avalonia.Skia.RenderTests
             CompareImages();
         }
 
+        [Fact]
+        public async Task Border_BackgroundSizing_OuterBorderEdge()
+        {
+            Decorator target = new Decorator
+            {
+                Padding = new Thickness(8),
+                Width = 240,
+                Height = 200,
+                Child = new Border
+                {
+                    Width = 160,
+                    Height = 120,
+                    Background = Brushes.CornflowerBlue,
+                    BackgroundSizing = BackgroundSizing.OuterBorderEdge,
+                    BorderBrush = Brushes.Black,
+                    BorderThickness = new Thickness(20),
+                    CornerRadius = new CornerRadius(24)
+                }
+            };
+
+            await RenderToFile(target);
+            CompareImages();
+        }
+
         [Fact]
         public async Task Border_Brush_Offsets_Content()
         {

tests/Avalonia.RenderTests/Controls/ContentPresenterTests.cs

@@ -44,4 +44,28 @@ public class ContentPresenterTests : TestBase
         await RenderToFile(target);
         CompareImages();
     }
+
+    [Fact]
+    public async Task ContentPresenter_BackgroundSizing_OuterBorderEdge()
+    {
+        Decorator target = new Decorator
+        {
+            Padding = new Thickness(8),
+            Width = 240,
+            Height = 200,
+            Child = new ContentPresenter
+            {
+                Width = 160,
+                Height = 120,
+                Background = Brushes.CornflowerBlue,
+                BackgroundSizing = BackgroundSizing.OuterBorderEdge,
+                BorderBrush = Brushes.Black,
+                BorderThickness = new Thickness(20),
+                CornerRadius = new CornerRadius(24)
+            }
+        };
+
+        await RenderToFile(target);
+        CompareImages();
+    }
 }