use FormattableString for .DebugSave(...) and .CompareToReferenceOutput(...) whenever possible

tests/ImageSharp.Tests/Processing/Transforms/AffineTransformTests.cs

@@ -118,7 +118,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Transforms
 
                 image.Mutate(i => i.Transform(m, KnownResamplers.Bicubic));
 
-                string testOutputDetails = $"R({angleDeg})_S({sx},{sy})_T({tx},{ty})";
+                FormattableString testOutputDetails = $"R({angleDeg})_S({sx},{sy})_T({tx},{ty})";
                 image.DebugSave(provider, testOutputDetails);
                 image.CompareToReferenceOutput(ValidatorComparer, provider, testOutputDetails);
             }
@@ -135,7 +135,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Transforms
 
                 image.Mutate(i => i.Transform(m, KnownResamplers.Bicubic));
 
-                string testOutputDetails = $"R({angleDeg})_S({s})";
+                FormattableString testOutputDetails = $"R({angleDeg})_S({s})";
                 image.DebugSave(provider, testOutputDetails);
                 image.CompareToReferenceOutput(ValidatorComparer, provider, testOutputDetails);
             }

tests/ImageSharp.Tests/TestUtilities/ImagingTestCaseUtility.cs

@@ -111,7 +111,11 @@ namespace SixLabors.ImageSharp.Tests
         {
             string detailsString = null;
 
-            if (testOutputDetails is string s)
+            if (testOutputDetails is FormattableString fs)
+            {
+                detailsString = fs.AsInvariantString();
+            }
+            else if (testOutputDetails is string s)
             {
                 detailsString = s;
             }

tests/ImageSharp.Tests/TestUtilities/TestImageExtensions.cs

@@ -52,6 +52,23 @@ namespace SixLabors.ImageSharp.Tests
             });
         }
 
+        public static Image<TPixel> DebugSave<TPixel>(
+            this Image<TPixel> image,
+            ITestImageProvider provider,
+            FormattableString testOutputDetails,
+            string extension = "png",
+            bool appendPixelTypeToFileName = true,
+            bool appendSourceFileOrDescription = true)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            return image.DebugSave(
+                provider,
+                (object)testOutputDetails,
+                extension,
+                appendPixelTypeToFileName,
+                appendSourceFileOrDescription);
+        }
+
         /// <summary>
         /// Saves the image only when not running in the CI server.
         /// </summary>
@@ -86,6 +103,17 @@ namespace SixLabors.ImageSharp.Tests
             return image;
         }
 
+        public static Image<TPixel> DebugSave<TPixel>(
+            this Image<TPixel> image,
+            ITestImageProvider provider,
+            IImageEncoder encoder,
+            FormattableString testOutputDetails,
+            bool appendPixelTypeToFileName = true)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            return image.DebugSave(provider, encoder, (object)testOutputDetails, appendPixelTypeToFileName);
+        }
+
         /// <summary>
         /// Saves the image only when not running in the CI server.
         /// </summary>
@@ -139,6 +167,23 @@ namespace SixLabors.ImageSharp.Tests
             return image;
         }
 
+        public static Image<TPixel> CompareToReferenceOutput<TPixel>(
+            this Image<TPixel> image,
+            ITestImageProvider provider,
+            FormattableString testOutputDetails,
+            string extension = "png",
+            bool grayscale = false,
+            bool appendPixelTypeToFileName = true)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            return image.CompareToReferenceOutput(
+                provider,
+                (object)testOutputDetails,
+                extension,
+                grayscale,
+                appendPixelTypeToFileName);
+        }
+
         /// <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)"/>.
@@ -150,7 +195,6 @@ namespace SixLabors.ImageSharp.Tests
         /// <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="appendPixelTypeToFileName">A boolean indicating whether to append the pixel type to the  output file name.</param>
-        /// <param name="comparer">A custom <see cref="ImageComparer"/> for the verification</param>
         /// <returns></returns>
         public static Image<TPixel> CompareToReferenceOutput<TPixel>(
             this Image<TPixel> image,
@@ -171,6 +215,25 @@ namespace SixLabors.ImageSharp.Tests
                 appendPixelTypeToFileName);
         }
 
+        public static Image<TPixel> CompareToReferenceOutput<TPixel>(
+            this Image<TPixel> image,
+            ImageComparer comparer,
+            ITestImageProvider provider,
+            FormattableString testOutputDetails,
+            string extension = "png",
+            bool grayscale = false,
+            bool appendPixelTypeToFileName = true)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            return image.CompareToReferenceOutput(
+                comparer,
+                provider,
+                (object)testOutputDetails,
+                extension,
+                grayscale,
+                appendPixelTypeToFileName);
+        }
+
         /// <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)"/>.