Set expected default configuration count to 5

tests/ImageSharp.Tests/ConfigurationTests.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Six Labors and contributors.
+// Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
 using System;
@@ -20,6 +20,8 @@ namespace SixLabors.ImageSharp.Tests
         public Configuration ConfigurationEmpty { get; }
         public Configuration DefaultConfiguration { get; }
 
+        private readonly int expectedDefaultConfigurationCount = 5;
+
         public ConfigurationTests()
         {
             // the shallow copy of configuration should behave exactly like the default configuration,
@@ -92,14 +94,13 @@ namespace SixLabors.ImageSharp.Tests
         [Fact]
         public void ConfigurationCannotAddDuplicates()
         {
-            const int count = 4;
             Configuration config = this.DefaultConfiguration;
 
-            Assert.Equal(count, config.ImageFormats.Count());
+            Assert.Equal(expectedDefaultConfigurationCount, config.ImageFormats.Count());
 
             config.ImageFormatsManager.AddImageFormat(BmpFormat.Instance);
 
-            Assert.Equal(count, config.ImageFormats.Count());
+            Assert.Equal(expectedDefaultConfigurationCount, config.ImageFormats.Count());
         }
 
         [Fact]
@@ -107,7 +108,7 @@ namespace SixLabors.ImageSharp.Tests
         {
             Configuration config = Configuration.CreateDefaultInstance();
 
-            Assert.Equal(4, config.ImageFormats.Count());
+            Assert.Equal(expectedDefaultConfigurationCount, config.ImageFormats.Count());
         }
 
         [Fact]
@@ -117,4 +118,4 @@ namespace SixLabors.ImageSharp.Tests
             Assert.True(config.WorkingBufferSizeHintInBytes  > 1024);
         }
     }
-}
+}