Use Magick Reference Decoder for Encode_Lossy_WithAlpha_Works

tests/ImageSharp.Tests/Formats/WebP/WebpEncoderTests.cs

@@ -7,6 +7,7 @@ using SixLabors.ImageSharp.Metadata;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Tests.TestUtilities;
 using SixLabors.ImageSharp.Tests.TestUtilities.ImageComparison;
+using SixLabors.ImageSharp.Tests.TestUtilities.ReferenceCodecs;
 using Xunit;
 using static SixLabors.ImageSharp.Tests.TestImages.Webp;
 
@@ -280,7 +281,13 @@ namespace SixLabors.ImageSharp.Tests.Formats.Webp
             };
 
             using Image<TPixel> image = provider.GetImage();
-            image.VerifyEncoder(provider, "webp", $"with_alpha_compressed_{compressed}", encoder, ImageComparer.Tolerant(0.04f));
+            image.VerifyEncoder(
+                provider,
+                "webp",
+                $"with_alpha_compressed_{compressed}",
+                encoder,
+                ImageComparer.Tolerant(0.04f),
+                referenceDecoder: new MagickReferenceDecoder());
         }
 
         [Theory]

tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/MagickReferenceDecoder.cs

@@ -26,7 +26,7 @@ namespace SixLabors.ImageSharp.Tests.TestUtilities.ReferenceCodecs
 
         public MagickReferenceDecoder(bool validate) => this.validate = validate;
 
-        public static MagickReferenceDecoder Instance { get; } = new MagickReferenceDecoder();
+        public static MagickReferenceDecoder Instance { get; } = new();
 
         private static void FromRgba32Bytes<TPixel>(Configuration configuration, Span<byte> rgbaBytes, IMemoryGroup<TPixel> destinationGroup)
             where TPixel : unmanaged, ImageSharp.PixelFormats.IPixel<TPixel>