Add another unit test to ensure the recent changes

don't get lost at some point in time

tests/Avalonia.Base.UnitTests/Media/DrawingGroupTests.cs

@@ -0,0 +1,99 @@
+using Avalonia.Media;
+using Avalonia.Platform;
+using Avalonia.Rendering.SceneGraph;
+using Avalonia.UnitTests;
+using Avalonia.Utilities;
+using Moq;
+using Xunit;
+
+namespace Avalonia.Base.UnitTests.Media;
+
+public class DrawingGroupTests
+{
+    [Fact]
+    public void PushEffect_Should_Store_Provided_Bounds()
+    {
+        using (UnitTestApplication.Start(new TestServices(renderInterface: Mock.Of<IPlatformRenderInterface>())))
+        {
+            var group = new DrawingGroup();
+            var effect = new BlurEffect { Radius = 10 };
+            var bounds = new Rect(10, 10, 100, 100);
+
+            using (var context = group.Open())
+            {
+                using (context.PushEffect(effect, bounds))
+                {
+                    context.DrawRectangle(Brushes.Red, null, new Rect(20, 20, 50, 50));
+                }
+            }
+
+            // The Open() call adds a child DrawingGroup to the root group when PushEffect is called.
+            Assert.Single(group.Children);
+            var childGroup = Assert.IsType<DrawingGroup>(group.Children[0]);
+            Assert.Equal(effect, childGroup.Effect);
+            Assert.Equal(bounds, childGroup.EffectBounds);
+        }
+    }
+
+    [Fact]
+    public void Drawing_With_Effect_Should_Use_Stored_Bounds()
+    {
+        using (UnitTestApplication.Start(new TestServices(renderInterface: Mock.Of<IPlatformRenderInterface>())))
+        {
+            var effect = new BlurEffect { Radius = 10 };
+            var bounds = new Rect(10, 10, 100, 100);
+            var group = new DrawingGroup
+            {
+                Effect = effect,
+                EffectBounds = bounds
+            };
+            group.Children.Add(new GeometryDrawing { Brush = Brushes.Red, Geometry = new RectangleGeometry { Rect = new Rect(20, 20, 50, 50) } });
+
+            var mockContext = new MockDrawingContext();
+            group.Draw(mockContext);
+
+            Assert.Equal(effect, mockContext.Effect);
+            Assert.Equal(bounds, mockContext.Bounds);
+        }
+    }
+
+    private class MockDrawingContext : DrawingContext
+    {
+        public IEffect? Effect { get; private set; }
+        public Rect Bounds { get; private set; }
+
+        protected override void PushEffectCore(IEffect effect, Rect bounds)
+        {
+            Effect = effect;
+            Bounds = bounds;
+        }
+
+        protected override void PopEffectCore() { }
+
+        // Implementing required abstract members
+        protected override void DrawEllipseCore(IBrush? brush, IPen? pen, Rect rect) { }
+        protected override void DrawGeometryCore(IBrush? brush, IPen? pen, IGeometryImpl geometry) { }
+        protected override void DrawLineCore(IPen pen, Point p1, Point p2) { }
+        protected override void DrawRectangleCore(IBrush? brush, IPen? pen, RoundedRect rrect, BoxShadows boxShadows = default) { }
+        protected override void PushClipCore(Rect rect) { }
+        protected override void PushClipCore(RoundedRect rect) { }
+        protected override void PushGeometryClipCore(Geometry clip) { }
+        protected override void PushOpacityCore(double opacity) { }
+        protected override void PushOpacityMaskCore(IBrush mask, Rect bounds) { }
+        protected override void PushTransformCore(Matrix matrix) { }
+        protected override void PopClipCore() { }
+        protected override void PopGeometryClipCore() { }
+        protected override void PopOpacityCore() { }
+        protected override void PopOpacityMaskCore() { }
+        protected override void PopTransformCore() { }
+
+        protected override void DisposeCore() { }
+        internal override void DrawBitmap(IRef<IBitmapImpl> source, double opacity, Rect sourceRect, Rect destRect) { }
+        public override void Custom(ICustomDrawOperation custom) { }
+        public override void DrawGlyphRun(IBrush? foreground, GlyphRun glyphRun) { }
+        protected override void PushRenderOptionsCore(RenderOptions renderOptions) { }
+        protected override void PushTextOptionsCore(TextOptions textOptions) { }
+        protected override void PopRenderOptionsCore() { }
+        protected override void PopTextOptionsCore() { }
+    }
+}