Add FormattedImage tests

Author: JimBobSquarePants

src/ImageSharp.Web/FormattedImage.cs

@@ -47,7 +47,7 @@ public IImageFormat Format
             {
                 if (value is null)
                 {
-                    ThrowInvalid(nameof(value));
+                    ThrowNull(nameof(value));
                 }
 
                 this.format = value;
@@ -65,7 +65,7 @@ public IImageEncoder Encoder
             {
                 if (value is null)
                 {
-                    ThrowInvalid(nameof(value));
+                    ThrowNull(nameof(value));
                 }
 
                 // The given type should match the format encoder.
@@ -108,6 +108,9 @@ public void Dispose()
         }
 
         [MethodImpl(MethodImplOptions.NoInlining)]
-        private static void ThrowInvalid(string name) => throw new ArgumentNullException(name);
+        private static void ThrowNull(string name) => throw new ArgumentNullException(name);
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static void ThrowInvalid(string name) => throw new ArgumentException(name);
     }
 }

tests/ImageSharp.Web.Tests/Processors/FormattedImageTests.cs

@@ -0,0 +1,72 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+using SixLabors.ImageSharp.Formats.Jpeg;
+using SixLabors.ImageSharp.Formats.Png;
+using SixLabors.ImageSharp.PixelFormats;
+using Xunit;
+
+namespace SixLabors.ImageSharp.Web.Tests.Processors
+{
+    public class FormattedImageTests
+    {
+        [Fact]
+        public void ConstructorSetsProperties()
+        {
+            using var image = new Image<Rgba32>(1, 1);
+            using var formatted = new FormattedImage(image, JpegFormat.Instance);
+
+            Assert.NotNull(formatted.Image);
+            Assert.Equal(image, formatted.Image);
+
+            Assert.NotNull(formatted.Format);
+            Assert.Equal(JpegFormat.Instance, formatted.Format);
+
+            Assert.NotNull(formatted.Encoder);
+            Assert.Equal(typeof(JpegEncoder), formatted.Encoder.GetType());
+        }
+
+        [Fact]
+        public void CanSetFormat()
+        {
+            using var image = new Image<Rgba32>(1, 1);
+            using var formatted = new FormattedImage(image, JpegFormat.Instance);
+
+            Assert.NotNull(formatted.Format);
+            Assert.Equal(JpegFormat.Instance, formatted.Format);
+
+            Assert.Throws<ArgumentNullException>(() => formatted.Format = null);
+
+            formatted.Format = PngFormat.Instance;
+            Assert.Equal(PngFormat.Instance, formatted.Format);
+            Assert.Equal(typeof(PngEncoder), formatted.Encoder.GetType());
+        }
+
+        [Fact]
+        public void CanSetEncoder()
+        {
+            using var image = new Image<Rgba32>(1, 1);
+            using var formatted = new FormattedImage(image, PngFormat.Instance);
+
+            Assert.NotNull(formatted.Format);
+            Assert.Equal(PngFormat.Instance, formatted.Format);
+
+            Assert.Throws<ArgumentNullException>(() => formatted.Encoder = null);
+            Assert.Throws<ArgumentException>(() => formatted.Encoder = new JpegEncoder());
+
+            formatted.Format = JpegFormat.Instance;
+            Assert.Equal(typeof(JpegEncoder), formatted.Encoder.GetType());
+
+            JpegSubsample current = ((JpegEncoder)formatted.Encoder).Subsample.GetValueOrDefault();
+
+            Assert.Equal(JpegSubsample.Ratio444, current);
+            formatted.Encoder = new JpegEncoder { Subsample = JpegSubsample.Ratio420 };
+
+            JpegSubsample replacement = ((JpegEncoder)formatted.Encoder).Subsample.GetValueOrDefault();
+
+            Assert.NotEqual(current, replacement);
+            Assert.Equal(JpegSubsample.Ratio420, replacement);
+        }
+    }
+}