[SL.Core] Add HashHelpersTests

src/SixLabors.Core/Helpers/HashHelpers.cs

@@ -59,4 +59,4 @@ namespace SixLabors
             return hash;
         }
     }
-}
+}

tests/SixLabors.Core.Tests/Helpers/HashHelpersTests.cs

@@ -0,0 +1,28 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using Xunit;
+
+namespace SixLabors.Tests.Helpers
+{
+    public class HashHelpersTests
+    {
+        [Fact]
+        public void CanCombineTwoValues()
+        {
+            Assert.Equal(35, HashHelpers.Combine(1, 2));
+        }
+
+        [Fact]
+        public void CanCombineThreeValues()
+        {
+            Assert.Equal(1152, HashHelpers.Combine(1, 2, 3));
+        }
+
+        [Fact]
+        public void CanCombineFourValues()
+        {
+            Assert.Equal(38020, HashHelpers.Combine(1, 2, 3, 4));
+        }
+    }
+}