diff --git a/tests/ImageSharp.Tests/TestUtilities/ImageComparison/TolerantImageComparer.cs b/tests/ImageSharp.Tests/TestUtilities/ImageComparison/TolerantImageComparer.cs
index 27feb046f..bc938ca0c 100644
--- a/tests/ImageSharp.Tests/TestUtilities/ImageComparison/TolerantImageComparer.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/ImageComparison/TolerantImageComparer.cs
@@ -2,6 +2,7 @@
 {
     using System;
     using System.Collections.Generic;
+    using System.Runtime.CompilerServices;
 
     using ImageSharp.PixelFormats;
 
@@ -90,11 +91,13 @@
             }
         }
 
-
-        private static int GetDifferenceInPixelByteSum(ref Rgba32 expected, ref Rgba32 actual)
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static int GetDifferenceInPixelByteSum(ref Rgba32 a, ref Rgba32 b)
         {
-            return (int)actual.R - (int)expected.R + (int)actual.G - (int)expected.G + (int)actual.B - (int)expected.B
-                   + (int)actual.A - (int)expected.A;
+            return Diff(a.R, b.R) + Diff(a.G, b.G) + Diff(a.B, b.B) + Diff(a.A, b.A);
         }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static int Diff(byte a, byte b) => Math.Abs(a - b);
     }
 }
\ No newline at end of file
diff --git a/tests/ImageSharp.Tests/TestUtilities/TestEnvironment.cs b/tests/ImageSharp.Tests/TestUtilities/TestEnvironment.cs
index ce61172e2..728cf4569 100644
--- a/tests/ImageSharp.Tests/TestUtilities/TestEnvironment.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/TestEnvironment.cs
@@ -15,7 +15,7 @@ namespace ImageSharp.Tests
 
         private const string ActualOutputDirectoryRelativePath = @"tests\Images\ActualOutput";
 
-        private const string ReferenceOutputDirectoryRelativePath = @"tests\Images\ReferenceOutput";
+        private const string ReferenceOutputDirectoryRelativePath = @"tests\Images\External\ReferenceOutput";
 
         private static Lazy<string> solutionDirectoryFullPath = new Lazy<string>(GetSolutionDirectoryFullPathImpl);
 
@@ -79,6 +79,6 @@ namespace ImageSharp.Tests
         internal static string ReferenceOutputDirectoryFullPath => Path.Combine(SolutionDirectoryFullPath, ReferenceOutputDirectoryRelativePath);
 
         internal static string GetReferenceOutputFileName(string actualOutputFileName) =>
-            actualOutputFileName.Replace("ActualOutput", "ReferenceOutput");
+            actualOutputFileName.Replace("ActualOutput", @"External\ReferenceOutput");
     }
 }
\ No newline at end of file
diff --git a/tests/ImageSharp.Tests/TestUtilities/TestImageExtensions.cs b/tests/ImageSharp.Tests/TestUtilities/TestImageExtensions.cs
index fe70e6cc1..41619a3d2 100644
--- a/tests/ImageSharp.Tests/TestUtilities/TestImageExtensions.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/TestImageExtensions.cs
@@ -6,10 +6,7 @@
 namespace ImageSharp.Tests
 {
     using System;
-    using System.Collections.Generic;
     using System.IO;
-    using System.Linq;
-    using System.Reflection;
 
     using ImageSharp.PixelFormats;
     using ImageSharp.Tests.TestUtilities.ImageComparison;
@@ -38,7 +35,7 @@ namespace ImageSharp.Tests
             {
                 return image;
             }
-            
+
             // We are running locally then we want to save it out
             provider.Utility.SaveTestOutputFile(
                 image,
@@ -55,10 +52,10 @@ namespace ImageSharp.Tests
         /// <typeparam name="TPixel">The pixel format</typeparam>
         /// <param name="image">The image</param>
         /// <param name="provider">The image provider</param>
+        /// <param name="comparer">The <see cref="ImageComparer"/> to use</param>
         /// <param name="testOutputDetails">Details to be concatenated to the test output file, describing the parameters of the test.</param>
         /// <param name="extension">The extension</param>
         /// <param name="grayscale">A boolean indicating whether we should debug save + compare against a grayscale image, smaller in size.</param>
-        /// <param name="customImageComparer">A custom <see cref="ImageComparer"/> if exact equlity is not the expected behaviour</param>
         /// <returns></returns>
         public static Image<TPixel> CompareToReferenceOutput<TPixel>(
             this Image<TPixel> image,
@@ -67,6 +64,36 @@ namespace ImageSharp.Tests
             string extension = "png",
             bool grayscale = false)
             where TPixel : struct, IPixel<TPixel>
+        {
+            return CompareToReferenceOutput(
+                image,
+                provider,
+                ImageComparer.Tolerant(),
+                testOutputDetails,
+                extension,
+                grayscale);
+        }
+
+        /// <summary>
+        /// Compares the image against the expected Reference output, throws an exception if the images are not similar enough.
+        /// The output file should be named identically to the output produced by <see cref="DebugSave{TPixel}(Image{TPixel}, ITestImageProvider, object, string, bool)"/>.
+        /// </summary>
+        /// <typeparam name="TPixel">The pixel format</typeparam>
+        /// <param name="image">The image</param>
+        /// <param name="provider">The image provider</param>
+        /// <param name="comparer">The <see cref="ImageComparer"/> to use</param>
+        /// <param name="testOutputDetails">Details to be concatenated to the test output file, describing the parameters of the test.</param>
+        /// <param name="extension">The extension</param>
+        /// <param name="grayscale">A boolean indicating whether we should debug save + compare against a grayscale image, smaller in size.</param>
+        /// <returns></returns>
+        public static Image<TPixel> CompareToReferenceOutput<TPixel>(
+            this Image<TPixel> image,
+            ITestImageProvider provider,
+            ImageComparer comparer,
+            object testOutputDetails = null,
+            string extension = "png",
+            bool grayscale = false)
+            where TPixel : struct, IPixel<TPixel>
         {
             string referenceOutputFile = provider.Utility.GetReferenceOutputFileName(extension, testOutputDetails);
 
@@ -86,11 +113,10 @@ namespace ImageSharp.Tests
 
             using (Image<Rgba32> referenceImage = Image.Load<Rgba32>(referenceOutputFile, ReferenceDecoder.Instance))
             {
-                ImageComparer comparer = ImageComparer.Exact;
-                comparer.CompareImages(referenceImage, image);
+                comparer.VerifySimilarity(referenceImage, image);
             }
-            
+
             return image;
         }
     }
-}
+}
\ No newline at end of file
diff --git a/tests/ImageSharp.Tests/TestUtilities/Tests/ImageComparerTests.cs b/tests/ImageSharp.Tests/TestUtilities/Tests/ImageComparerTests.cs
index 8bb26ad17..799bd822a 100644
--- a/tests/ImageSharp.Tests/TestUtilities/Tests/ImageComparerTests.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/Tests/ImageComparerTests.cs
@@ -90,7 +90,7 @@ namespace ImageSharp.Tests
         }
 
         [Theory]
-        [WithTestPatternImages(100, 100, PixelTypes.Rgba32)]
+        [WithTestPatternImages(110, 110, PixelTypes.Rgba32)]
         public void TolerantImageComparer_ApprovesSimilarityBelowTolerance<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : struct, IPixel<TPixel>
         {
diff --git a/tests/ImageSharp.Tests/TestUtilities/Tests/TestImageExtensionsTests.cs b/tests/ImageSharp.Tests/TestUtilities/Tests/TestImageExtensionsTests.cs
new file mode 100644
index 000000000..1a5e85646
--- /dev/null
+++ b/tests/ImageSharp.Tests/TestUtilities/Tests/TestImageExtensionsTests.cs
@@ -0,0 +1,47 @@
+// ReSharper disable InconsistentNaming
+namespace ImageSharp.Tests
+{
+    using System;
+
+    using ImageSharp.PixelFormats;
+
+    using Xunit;
+
+    public class TestImageExtensionsTests
+    {
+        [Theory]
+        [WithSolidFilledImages(10, 10, 0, 0, 255, PixelTypes.Rgba32)]
+        public void CompareToReferenceOutput_WhenReferenceOutputMatches_ShouldNotThrow<TPixel>(
+            TestImageProvider<TPixel> provider)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            using (Image<TPixel> image = provider.GetImage())
+            {
+                image.CompareToReferenceOutput(provider);
+            }
+        }
+
+        [Theory]
+        [WithSolidFilledImages(10, 10, 0, 0, 255, PixelTypes.Rgba32)]
+        public void CompareToReferenceOutput_WhenReferenceOutputDoesNotMatch_Throws<TPixel>(
+            TestImageProvider<TPixel> provider)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            using (Image<TPixel> image = provider.GetImage())
+            {
+                Assert.ThrowsAny<Exception>(() => image.CompareToReferenceOutput(provider));
+            }
+        }
+
+        [Theory]
+        [WithSolidFilledImages(10, 10, 0, 0, 255, PixelTypes.Rgba32)]
+        public void CompareToReferenceOutput_WhenReferenceFileMissing_Throws<TPixel>(TestImageProvider<TPixel> provider)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            using (Image<TPixel> image = provider.GetImage())
+            {
+                Assert.ThrowsAny<Exception>(() => image.CompareToReferenceOutput(provider));
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/tests/Images/External b/tests/Images/External
index 8240bdb29..ec2161042 160000
--- a/tests/Images/External
+++ b/tests/Images/External
@@ -1 +1 @@
-Subproject commit 8240bdb291e3476c4e50fef6fe2fccfe4fbd10c4
+Subproject commit ec2161042fe9addeff10fab73b0a3d71172b86a8