more missing stubs.

tests/Avalonia.Visuals.UnitTests/VisualTree/MockRenderInterface.cs

@@ -42,6 +42,28 @@ namespace Avalonia.Visuals.UnitTests.VisualTree
             throw new NotImplementedException();
         }
 
+        public IWriteableBitmapImpl LoadWriteableBitmapToWidth(Stream stream, int width,
+            BitmapInterpolationMode interpolationMode = BitmapInterpolationMode.HighQuality)
+        {
+            throw new NotImplementedException();
+        }
+
+        public IWriteableBitmapImpl LoadWriteableBitmapToHeight(Stream stream, int height,
+            BitmapInterpolationMode interpolationMode = BitmapInterpolationMode.HighQuality)
+        {
+            throw new NotImplementedException();
+        }
+
+        public IWriteableBitmapImpl LoadWriteableBitmap(string fileName)
+        {
+            throw new NotImplementedException();
+        }
+
+        public IWriteableBitmapImpl LoadWriteableBitmap(Stream stream)
+        {
+            throw new NotImplementedException();
+        }
+
         public IBitmapImpl LoadBitmap(string fileName)
         {
             throw new NotImplementedException();