Fix assignment of configuration options in unit tests

src/ImageSharp/Formats/DecoderOptions.cs

@@ -15,6 +15,11 @@ public sealed class DecoderOptions
 
     private uint maxFrames = int.MaxValue;
 
+    // Used by the FileProvider in the unit tests to set the configuration on the fly.
+#pragma warning disable SA1401 // Fields should be private
+    internal Configuration BackingConfiguration = Configuration.Default;
+#pragma warning restore SA1401 // Fields should be private
+
     /// <summary>
     /// Gets the shared default general decoder options instance.
     /// Used internally to reduce allocations for default decoding operations.
@@ -24,7 +29,7 @@ public sealed class DecoderOptions
     /// <summary>
     /// Gets a custom configuration instance to be used by the image processing pipeline.
     /// </summary>
-    public Configuration Configuration { get; init; } = Configuration.Default;
+    public Configuration Configuration { get => this.BackingConfiguration; init => this.BackingConfiguration = value; }
 
     /// <summary>
     /// Gets the target size to decode the image into. Scaling should use an operation equivalent to <see cref="ResizeMode.Max"/>.
@@ -46,3 +51,9 @@ public sealed class DecoderOptions
     /// </summary>
     public uint MaxFrames { get => this.maxFrames; init => this.maxFrames = Math.Clamp(value, 1, int.MaxValue); }
 }
+
+internal static class DecoderOptionsExtensions
+{
+    public static void SetConfiguration(this DecoderOptions options, Configuration configuration)
+        => options.BackingConfiguration = configuration;
+}

tests/ImageSharp.Tests/TestUtilities/ImageProviders/FileProvider.cs

@@ -207,7 +207,7 @@ public abstract partial class TestImageProvider<TPixel> : IXunitSerializable
             Guard.NotNull(decoder, nameof(decoder));
             Guard.NotNull(options, nameof(options));
 
-            options.Configuration = this.Configuration;
+            options.SetConfiguration(this.Configuration);
 
             // Used in small subset of decoder tests, no caching.
             // TODO: Check Path here. Why combined?
@@ -244,7 +244,7 @@ public abstract partial class TestImageProvider<TPixel> : IXunitSerializable
             Guard.NotNull(decoder, nameof(decoder));
             Guard.NotNull(options, nameof(options));
 
-            options.GeneralOptions.Configuration = this.Configuration;
+            options.GeneralOptions.SetConfiguration(this.Configuration);
 
             // Used in small subset of decoder tests, no caching.
             // TODO: Check Path here. Why combined?
@@ -268,7 +268,7 @@ public abstract partial class TestImageProvider<TPixel> : IXunitSerializable
 
         private Image<TPixel> DecodeImage(IImageDecoder decoder, DecoderOptions options)
         {
-            options.Configuration = this.Configuration;
+            options.SetConfiguration(this.Configuration);
 
             var testFile = TestFile.Create(this.FilePath);
             using Stream stream = new MemoryStream(testFile.Bytes);
@@ -278,7 +278,7 @@ public abstract partial class TestImageProvider<TPixel> : IXunitSerializable
         private Image<TPixel> DecodeImage<T>(ISpecializedImageDecoder<T> decoder, T options)
             where T : class, ISpecializedDecoderOptions, new()
         {
-            options.GeneralOptions.Configuration = this.Configuration;
+            options.GeneralOptions.SetConfiguration(this.Configuration);
 
             var testFile = TestFile.Create(this.FilePath);
             using Stream stream = new MemoryStream(testFile.Bytes);