Adding color constructor tests.

tests/ImageSharp.Tests/Colors/ColorConstructorTests.cs

@@ -0,0 +1,42 @@
+// <copyright file="ColorConstructorTests.cs" company="James Jackson-South">
+// Copyright (c) James Jackson-South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageSharp.Tests.Colors
+{
+    using System.Numerics;
+    using Xunit;
+
+    public class ColorConstructorTests
+    {
+        public static readonly TheoryData<object, Vector4> ColorData =
+            new TheoryData<object, Vector4>()
+            {
+                { new Alpha8(.5F), new Vector4(0, 0, 0, .5F) },
+                { new Argb(Vector4.One), Vector4.One },
+                { new Argb(Vector4.Zero), Vector4.Zero },
+                { new Argb(Vector4.UnitX), Vector4.UnitX },
+                { new Argb(Vector4.UnitY), Vector4.UnitY },
+                { new Argb(Vector4.UnitZ), Vector4.UnitZ },
+                { new Argb(Vector4.UnitW), Vector4.UnitW },
+            };
+
+        [Theory]
+        [MemberData(nameof(ColorData))]
+        public void ConstructorToVector4(IPackedVector color, Vector4 expectedVector4)
+        {
+            // Arrange
+            var precision = 2;
+
+            // Act
+            var vector4 = color.ToVector4();
+
+            // Assert
+            Assert.Equal(expectedVector4.X, vector4.X, precision);
+            Assert.Equal(expectedVector4.Y, vector4.Y, precision);
+            Assert.Equal(expectedVector4.Z, vector4.Z, precision);
+            Assert.Equal(expectedVector4.W, vector4.W, precision);
+        }
+    }
+}