looks like ApplyOilPaintFilterInBox() is failing with a very good reason

tests/ImageSharp.Tests/Processing/Processors/Effects/OilPaintTest.cs

@@ -22,7 +22,7 @@ namespace ImageSharp.Tests.Processing.Processors.Effects
 
         [Theory]
         [WithFileCollection(nameof(DefaultFiles), nameof(OilPaintValues), DefaultPixelType)]
-        public void ImageShouldApplyOilPaintFilter<TPixel>(TestImageProvider<TPixel> provider, int levels, int brushSize)
+        public void ApplyOilPaintFilter<TPixel>(TestImageProvider<TPixel> provider, int levels, int brushSize)
             where TPixel : struct, IPixel<TPixel>
         {
             using (Image<TPixel> image = provider.GetImage())
@@ -34,7 +34,7 @@ namespace ImageSharp.Tests.Processing.Processors.Effects
 
         [Theory]
         [WithFileCollection(nameof(DefaultFiles), nameof(OilPaintValues), DefaultPixelType)]
-        public void ImageShouldApplyOilPaintFilterInBox<TPixel>(TestImageProvider<TPixel> provider, int levels, int brushSize)
+        public void ApplyOilPaintFilterInBox<TPixel>(TestImageProvider<TPixel> provider, int levels, int brushSize)
             where TPixel : struct, IPixel<TPixel>
         {
             using (Image<TPixel> source = provider.GetImage())

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

@@ -10,9 +10,24 @@ namespace ImageSharp.Tests.TestUtilities.ImageComparison
         public ImageSimilarityReport[] Reports { get; }
 
         public ImagePixelsAreDifferentException(IEnumerable<ImageSimilarityReport> reports)
-            : base("Images are not similar enough! See 'Reports' for more details! ")
+            : base("Images are not similar enough!" + StringifyReports(reports))
         {
             this.Reports = reports.ToArray();
         }
+
+        private static string StringifyReports(IEnumerable<ImageSimilarityReport> reports)
+        {
+            StringBuilder sb = new StringBuilder();
+            sb.Append(Environment.NewLine);
+
+            int i = 0;
+            foreach (ImageSimilarityReport r in reports)
+            {
+                sb.Append($"Report{i}: ");
+                sb.Append(r);
+                sb.Append(Environment.NewLine);
+            }
+            return sb.ToString();
+        }
     }
 }

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

@@ -29,7 +29,7 @@
         {
             return this.IsEmpty ? "[SimilarImages]" : StringifyDifferences(this.Differences);
         }
-
+        
         private static string StringifyDifferences(PixelDifference[] differences)
         {
             var sb = new StringBuilder();

tests/ImageSharp.Tests/TestUtilities/PixelTypes.cs

@@ -60,7 +60,6 @@ namespace ImageSharp.Tests
 
         // TODO: Add multi-flag entries by rules defined in PackedPixelConverterHelper
 
-        Default = Rgba32,
         // "All" is handled as a separate, individual case instead of using bitwise OR
         All = 30
     }

tests/ImageSharp.Tests/TestUtilities/Tests/ImageComparerTests.cs

@@ -115,10 +115,17 @@ namespace ImageSharp.Tests
             {
                 using (Image<TPixel> clone = image.Clone())
                 {
-                    ModifyPixel(clone, 0, 0, 2);
+                    ModifyPixel(clone, 3, 1, 2);
 
                     var comparer = ImageComparer.Tolerant();
-                    comparer.VerifySimilarity(image, clone);
+
+                    ImagePixelsAreDifferentException ex = Assert.ThrowsAny<ImagePixelsAreDifferentException>(
+                        () =>
+                            {
+                                comparer.VerifySimilarity(image, clone);
+                            });
+                    PixelDifference diff = ex.Reports.Single().Differences.Single();
+                    Assert.Equal(new Point(3, 1), diff.Position);
                 }
             }
         }