Better fix for report

tests/ImageSharp.Tests/TestUtilities/ImageComparison/ExactImageComparer.cs

@@ -12,6 +12,7 @@ public class ExactImageComparer : ImageComparer
     public static ExactImageComparer Instance { get; } = new ExactImageComparer();
 
     public override ImageSimilarityReport<TPixelA, TPixelB> CompareImagesOrFrames<TPixelA, TPixelB>(
+        int index,
         ImageFrame<TPixelA> expected,
         ImageFrame<TPixelB> actual)
     {
@@ -52,6 +53,6 @@ public class ExactImageComparer : ImageComparer
             }
         }
 
-        return new ImageSimilarityReport<TPixelA, TPixelB>(expected, actual, differences);
+        return new ImageSimilarityReport<TPixelA, TPixelB>(index, expected, actual, differences);
     }
 }

tests/ImageSharp.Tests/TestUtilities/ImageComparison/Exceptions/ImageDifferenceIsOverThresholdException.cs

@@ -33,13 +33,11 @@ public class ImageDifferenceIsOverThresholdException : ImagesSimilarityException
         sb.AppendFormat("Test Environment is Mono : {0}", TestEnvironment.IsMono);
         sb.Append(Environment.NewLine);
 
-        int i = 0;
         foreach (ImageSimilarityReport r in reports)
         {
-            sb.Append($"Report ImageFrame {i}: ");
+            sb.AppendFormat("Report ImageFrame {0}: ", r.Index);
             sb.Append(r);
             sb.Append(Environment.NewLine);
-            i++;
         }
 
         return sb.ToString();

tests/ImageSharp.Tests/TestUtilities/ImageComparison/ImageComparer.cs

@@ -27,6 +27,7 @@ public abstract class ImageComparer
         => Tolerant(imageThresholdInPercents / 100F, perPixelManhattanThreshold);
 
     public abstract ImageSimilarityReport<TPixelA, TPixelB> CompareImagesOrFrames<TPixelA, TPixelB>(
+        int index,
         ImageFrame<TPixelA> expected,
         ImageFrame<TPixelB> actual)
         where TPixelA : unmanaged, IPixel<TPixelA>
@@ -40,7 +41,7 @@ public static class ImageComparerExtensions
         Image<TPixelA> expected,
         Image<TPixelB> actual)
         where TPixelA : unmanaged, IPixel<TPixelA>
-        where TPixelB : unmanaged, IPixel<TPixelB> => comparer.CompareImagesOrFrames(expected.Frames.RootFrame, actual.Frames.RootFrame);
+        where TPixelB : unmanaged, IPixel<TPixelB> => comparer.CompareImagesOrFrames(0, expected.Frames.RootFrame, actual.Frames.RootFrame);
 
     public static IEnumerable<ImageSimilarityReport<TPixelA, TPixelB>> CompareImages<TPixelA, TPixelB>(
         this ImageComparer comparer,
@@ -58,7 +59,7 @@ public static class ImageComparerExtensions
 
         for (int i = 0; i < expected.Frames.Count; i++)
         {
-            ImageSimilarityReport<TPixelA, TPixelB> report = comparer.CompareImagesOrFrames(expected.Frames[i], actual.Frames[i]);
+            ImageSimilarityReport<TPixelA, TPixelB> report = comparer.CompareImagesOrFrames(i, expected.Frames[i], actual.Frames[i]);
             if (!report.IsEmpty)
             {
                 result.Add(report);
@@ -125,7 +126,7 @@ public static class ImageComparerExtensions
 
                 if (outsideChanges.Any())
                 {
-                    cleanedReports.Add(new ImageSimilarityReport<TPixelA, TPixelB>(r.ExpectedImage, r.ActualImage, outsideChanges, null));
+                    cleanedReports.Add(new ImageSimilarityReport<TPixelA, TPixelB>(r.Index, r.ExpectedImage, r.ActualImage, outsideChanges, null));
                 }
             }
 

tests/ImageSharp.Tests/TestUtilities/ImageComparison/ImageSimilarityReport.cs

@@ -9,17 +9,21 @@ namespace SixLabors.ImageSharp.Tests.TestUtilities.ImageComparison;
 public class ImageSimilarityReport
 {
     protected ImageSimilarityReport(
+        int index,
         object expectedImage,
         object actualImage,
         IEnumerable<PixelDifference> differences,
         float? totalNormalizedDifference = null)
     {
+        this.Index = index;
         this.ExpectedImage = expectedImage;
         this.ActualImage = actualImage;
         this.TotalNormalizedDifference = totalNormalizedDifference;
         this.Differences = differences.ToArray();
     }
 
+    public int Index { get; }
+
     public object ExpectedImage { get; }
 
     public object ActualImage { get; }
@@ -89,16 +93,17 @@ public class ImageSimilarityReport<TPixelA, TPixelB> : ImageSimilarityReport
     where TPixelB : unmanaged, IPixel<TPixelB>
 {
     public ImageSimilarityReport(
+        int index,
         ImageFrame<TPixelA> expectedImage,
         ImageFrame<TPixelB> actualImage,
         IEnumerable<PixelDifference> differences,
         float? totalNormalizedDifference = null)
-        : base(expectedImage, actualImage, differences, totalNormalizedDifference)
+        : base(index, expectedImage, actualImage, differences, totalNormalizedDifference)
     {
     }
 
     public static ImageSimilarityReport<TPixelA, TPixelB> Empty =>
-        new ImageSimilarityReport<TPixelA, TPixelB>(null, null, Enumerable.Empty<PixelDifference>(), 0f);
+        new ImageSimilarityReport<TPixelA, TPixelB>(0, null, null, Enumerable.Empty<PixelDifference>(), 0f);
 
     public new ImageFrame<TPixelA> ExpectedImage => (ImageFrame<TPixelA>)base.ExpectedImage;
 

tests/ImageSharp.Tests/TestUtilities/ImageComparison/TolerantImageComparer.cs

@@ -56,7 +56,7 @@ public class TolerantImageComparer : ImageComparer
     /// </summary>
     public int PerPixelManhattanThreshold { get; }
 
-    public override ImageSimilarityReport<TPixelA, TPixelB> CompareImagesOrFrames<TPixelA, TPixelB>(ImageFrame<TPixelA> expected, ImageFrame<TPixelB> actual)
+    public override ImageSimilarityReport<TPixelA, TPixelB> CompareImagesOrFrames<TPixelA, TPixelB>(int index, ImageFrame<TPixelA> expected, ImageFrame<TPixelB> actual)
     {
         if (expected.Size() != actual.Size())
         {
@@ -103,7 +103,7 @@ public class TolerantImageComparer : ImageComparer
 
         if (normalizedDifference > this.ImageThreshold)
         {
-            return new ImageSimilarityReport<TPixelA, TPixelB>(expected, actual, differences, normalizedDifference);
+            return new ImageSimilarityReport<TPixelA, TPixelB>(index, expected, actual, differences, normalizedDifference);
         }
         else
         {