Added unit tests for ExpressionFunctions.ColorLerpRgb and ColorLerpHsl

Author: Arlodotexe

components/Animations/tests/Animations.Tests.projitems

@@ -10,5 +10,6 @@
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="$(MSBuildThisFileDirectory)Test_AnimationBuilderStart.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Test_ExpressionFunctions.cs" />
   </ItemGroup>
 </Project>

components/Animations/tests/Test_AnimationBuilderStart.cs

@@ -9,7 +9,7 @@
 namespace AnimationsExperiment.Tests;
 
 [TestClass]
-[TestCategory("Test_AnimationBuilderStart")]
+[TestCategory(nameof(Test_AnimationBuilderStart))]
 public class Test_AnimationBuilderStart : VisualUITestBase
 {
     [TestMethod]

components/Animations/tests/Test_ExpressionFunctions.cs

@@ -0,0 +1,59 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#if WINUI2
+using Windows.UI.Composition;
+using Windows.UI.Xaml.Hosting;
+#elif WINUI3
+using Microsoft.UI.Composition;
+using Microsoft.UI.Xaml.Hosting;
+#endif
+
+using System.Numerics;
+using CommunityToolkit.Tests;
+using CommunityToolkit.Tooling.TestGen;
+using CommunityToolkit.WinUI.Animations.Expressions;
+
+namespace AnimationsExperiment.Tests;
+
+[TestClass]
+[TestCategory(nameof(Test_ExpressionFunctions))]
+public partial class Test_ExpressionFunctions : VisualUITestBase
+{
+    [UIThreadTestMethod]
+    public void ColorLerpRgb(Grid rootGrid)
+    {
+        // See https://github.com/CommunityToolkit/Windows/issues/303
+        var compositor = ElementCompositionPreview.GetElementVisual(rootGrid).Compositor;
+        var brush = compositor.CreateColorBrush();
+        var temp = ExpressionFunctions.ColorRgb(255f, 255f, 0f, 0f);
+        var color = ExpressionFunctions.ColorLerpRgb(temp, temp, 0.5f);
+
+        brush.StartAnimation("Color", color);
+
+        var visual = compositor.CreateSpriteVisual();
+        visual.Brush = brush;
+        visual.RelativeSizeAdjustment = Vector2.One;
+
+        ElementCompositionPreview.SetElementChildVisual(rootGrid, visual);
+    }
+
+    [UIThreadTestMethod]
+    public void ColorLerpHsl(Grid rootGrid)
+    {
+        // See https://github.com/CommunityToolkit/Windows/issues/303
+        var compositor = ElementCompositionPreview.GetElementVisual(rootGrid).Compositor;
+        var brush = compositor.CreateColorBrush();
+        var temp = ExpressionFunctions.ColorHsl(255f, 255f, 0f);
+        var color = ExpressionFunctions.ColorLerpHsl(temp, temp, 0.5f);
+
+        brush.StartAnimation("Color", color);
+
+        var visual = compositor.CreateSpriteVisual();
+        visual.Brush = brush;
+        visual.RelativeSizeAdjustment = Vector2.One;
+
+        ElementCompositionPreview.SetElementChildVisual(rootGrid, visual);
+    }
+}