diff --git a/tests/Avalonia.Visuals.UnitTests/Avalonia.Visuals.UnitTests.csproj b/tests/Avalonia.Visuals.UnitTests/Avalonia.Visuals.UnitTests.csproj
index 642172fe25..fd9fb82cfd 100644
--- a/tests/Avalonia.Visuals.UnitTests/Avalonia.Visuals.UnitTests.csproj
+++ b/tests/Avalonia.Visuals.UnitTests/Avalonia.Visuals.UnitTests.csproj
@@ -80,6 +80,8 @@
     <Compile Include="Media\FormattedTextTests.cs" />
     <Compile Include="Media\PathMarkupParserTests.cs" />
     <Compile Include="RelativeRectComparer.cs" />
+    <Compile Include="SizeTests.cs" />
+    <Compile Include="RectTests.cs" />
     <Compile Include="RelativeRectTests.cs" />
     <Compile Include="Rendering\DeferredRendererTests.cs" />
     <Compile Include="Rendering\SceneGraph\DeferredDrawingContextImplTests.cs" />
diff --git a/tests/Avalonia.Visuals.UnitTests/RectTests.cs b/tests/Avalonia.Visuals.UnitTests/RectTests.cs
new file mode 100644
index 0000000000..6e3f654bfb
--- /dev/null
+++ b/tests/Avalonia.Visuals.UnitTests/RectTests.cs
@@ -0,0 +1,42 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using Xunit;
+
+namespace Avalonia.Visuals.UnitTests
+{
+    public class RectTests
+    {
+        [Fact]
+        public void Union_Should_Return_Correct_Value_For_Intersecting_Rects()
+        {
+            var result = new Rect(0, 0, 100, 100).Union(new Rect(50, 50, 100, 100));
+
+            Assert.Equal(new Rect(0, 0, 150, 150), result);
+        }
+
+        [Fact]
+        public void Union_Should_Return_Correct_Value_For_NonIntersecting_Rects()
+        {
+            var result = new Rect(0, 0, 100, 100).Union(new Rect(150, 150, 100, 100));
+
+            Assert.Equal(new Rect(0, 0, 250, 250), result);
+        }
+
+        [Fact]
+        public void Union_Should_Ignore_Empty_This_rect()
+        {
+            var result = new Rect(0, 0, 0, 0).Union(new Rect(150, 150, 100, 100));
+
+            Assert.Equal(new Rect(150, 150, 100, 100), result);
+        }
+
+        [Fact]
+        public void Union_Should_Ignore_Empty_Other_rect()
+        {
+            var result = new Rect(0, 0, 100, 100).Union(new Rect(150, 150, 0, 0));
+
+            Assert.Equal(new Rect(0, 0, 100, 100), result);
+        }
+    }
+}
diff --git a/tests/Avalonia.Visuals.UnitTests/SizeTests.cs b/tests/Avalonia.Visuals.UnitTests/SizeTests.cs
new file mode 100644
index 0000000000..10a012bb7f
--- /dev/null
+++ b/tests/Avalonia.Visuals.UnitTests/SizeTests.cs
@@ -0,0 +1,26 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using Xunit;
+
+namespace Avalonia.Visuals.UnitTests
+{
+    public class SizeTests
+    {
+        [Fact]
+        public void Should_Produce_Correct_Aspect_Ratio()
+        {
+            var result = new Size(3, 2).AspectRatio;
+
+            Assert.Equal(1.5, result);
+        }
+
+        [Fact]
+        public void Dividing_Should_Produce_Scaling_Factor()
+        {
+            var result = new Size(15, 10) / new Size(5, 5);
+
+            Assert.Equal(new Vector(3, 2), result);
+        }
+    }
+}