add some tests for Viewbox

tests/Avalonia.Controls.UnitTests/ViewboxTests.cs

@@ -0,0 +1,105 @@
+using Avalonia.Controls.Shapes;
+using Avalonia.Media;
+using Xunit;
+
+namespace Avalonia.Controls.UnitTests
+{
+    public class ViewboxTests
+    {
+        [Fact]
+        public void Viewbox_Stretch_Uniform_Child()
+        {
+            var target = new Viewbox() { Child = new Rectangle() { Width = 100, Height = 50 } };
+
+            target.Measure(new Size(200, 200));
+            target.Arrange(new Rect(new Point(0, 0), target.DesiredSize));
+
+            Assert.Equal(new Size(200, 100), target.DesiredSize);
+            var scaleTransform = target.Child.RenderTransform as ScaleTransform;
+
+            Assert.NotNull(scaleTransform);
+            Assert.Equal(2.0, scaleTransform.ScaleX);
+            Assert.Equal(2.0, scaleTransform.ScaleY);
+        }
+
+        [Fact]
+        public void Viewbox_Stretch_None_Child()
+        {
+            var target = new Viewbox() { Stretch = Stretch.None, Child = new Rectangle() { Width = 100, Height = 50 } };
+
+            target.Measure(new Size(200, 200));
+            target.Arrange(new Rect(new Point(0, 0), target.DesiredSize));
+
+            Assert.Equal(new Size(100, 50), target.DesiredSize);
+            var scaleTransform = target.Child.RenderTransform as ScaleTransform;
+
+            Assert.NotNull(scaleTransform);
+            Assert.Equal(1.0, scaleTransform.ScaleX);
+            Assert.Equal(1.0, scaleTransform.ScaleY);
+        }
+
+        [Fact]
+        public void Viewbox_Stretch_Fill_Child()
+        {
+            var target = new Viewbox() { Stretch = Stretch.Fill, Child = new Rectangle() { Width = 100, Height = 50 } };
+
+            target.Measure(new Size(200, 200));
+            target.Arrange(new Rect(new Point(0, 0), target.DesiredSize));
+
+            Assert.Equal(new Size(200, 200), target.DesiredSize);
+            var scaleTransform = target.Child.RenderTransform as ScaleTransform;
+
+            Assert.NotNull(scaleTransform);
+            Assert.Equal(2.0, scaleTransform.ScaleX);
+            Assert.Equal(4.0, scaleTransform.ScaleY);
+        }
+
+        [Fact]
+        public void Viewbox_Stretch_UniformToFill_Child()
+        {
+            var target = new Viewbox() { Stretch = Stretch.UniformToFill, Child = new Rectangle() { Width = 100, Height = 50 } };
+
+            target.Measure(new Size(200, 200));
+            target.Arrange(new Rect(new Point(0, 0), target.DesiredSize));
+
+            Assert.Equal(new Size(200, 200), target.DesiredSize);
+            var scaleTransform = target.Child.RenderTransform as ScaleTransform;
+
+            Assert.NotNull(scaleTransform);
+            Assert.Equal(4.0, scaleTransform.ScaleX);
+            Assert.Equal(4.0, scaleTransform.ScaleY);
+        }
+
+        [Fact]
+        public void Viewbox_Stretch_Uniform_Child_With_Unrestricted_Width()
+        {
+            var target = new Viewbox() { Child = new Rectangle() { Width = 100, Height = 50 } };
+
+            target.Measure(new Size(double.PositiveInfinity, 200));
+            target.Arrange(new Rect(new Point(0, 0), target.DesiredSize));
+
+            Assert.Equal(new Size(400, 200), target.DesiredSize);
+            var scaleTransform = target.Child.RenderTransform as ScaleTransform;
+
+            Assert.NotNull(scaleTransform);
+            Assert.Equal(4.0, scaleTransform.ScaleX);
+            Assert.Equal(4.0, scaleTransform.ScaleY);
+        }
+
+        [Fact]
+        public void Viewbox_Stretch_Uniform_Child_With_Unrestricted_Height()
+        {
+            var target = new Viewbox() { Child = new Rectangle() { Width = 100, Height = 50 } };
+
+            target.Measure(new Size(200, double.PositiveInfinity));
+            target.Arrange(new Rect(new Point(0, 0), target.DesiredSize));
+
+            Assert.Equal(new Size(200, 100), target.DesiredSize);
+            var scaleTransform = target.Child.RenderTransform as ScaleTransform;
+
+            Assert.NotNull(scaleTransform);
+            Assert.Equal(2.0, scaleTransform.ScaleX);
+            Assert.Equal(2.0, scaleTransform.ScaleY);
+        }
+    }
+}