diff --git a/src/ImageSharp/Formats/ImageFormatsManager.cs b/src/ImageSharp/Formats/ImageFormatsManager.cs
index 3a78965612..350c28b0a3 100644
--- a/src/ImageSharp/Formats/ImageFormatsManager.cs
+++ b/src/ImageSharp/Formats/ImageFormatsManager.cs
@@ -1,4 +1,7 @@
-using System;
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Linq;
diff --git a/tests/ImageSharp.Tests/Formats/ImageFormatsManagerTests.cs b/tests/ImageSharp.Tests/Formats/ImageFormatsManagerTests.cs
new file mode 100644
index 0000000000..3aeeff9379
--- /dev/null
+++ b/tests/ImageSharp.Tests/Formats/ImageFormatsManagerTests.cs
@@ -0,0 +1,117 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using SixLabors.ImageSharp.Formats;
+using SixLabors.ImageSharp.IO;
+using SixLabors.ImageSharp.PixelFormats;
+using Moq;
+using Xunit;
+
+namespace SixLabors.ImageSharp.Tests
+{
+    public class ImageFormatsManagerTests
+    {
+        public ImageFormatsManager FormatsManagerEmpty { get; private set; }
+        public ImageFormatsManager DefaultFormatsManager { get; private set; }
+
+        public ImageFormatsManagerTests()
+        {
+            this.DefaultFormatsManager = Configuration.Default.FormatsManager;
+            this.FormatsManagerEmpty = new ImageFormatsManager();
+        }        
+
+        [Fact]
+        public void IfAutoloadWellknownFormatsIsTrueAllFormatsAreLoaded()
+        {
+            Assert.Equal(4, this.DefaultFormatsManager.ImageEncoders.Count());
+            Assert.Equal(4, this.DefaultFormatsManager.ImageDecoders.Count());
+        }
+
+        [Fact]
+        public void AddImageFormatDetectorNullthrows()
+        {
+            Assert.Throws<ArgumentNullException>(() =>
+            {
+                this.DefaultFormatsManager.AddImageFormatDetector(null);
+            });
+        }
+
+        [Fact]
+        public void RegisterNullMimeTypeEncoder()
+        {
+            Assert.Throws<ArgumentNullException>(() =>
+            {
+                this.DefaultFormatsManager.SetEncoder(null, new Mock<IImageEncoder>().Object);
+            });
+            Assert.Throws<ArgumentNullException>(() =>
+            {
+                this.DefaultFormatsManager.SetEncoder(ImageFormats.Bmp, null);
+            });
+            Assert.Throws<ArgumentNullException>(() =>
+            {
+                this.DefaultFormatsManager.SetEncoder(null, null);
+            });
+        }
+
+        [Fact]
+        public void RegisterNullSetDecoder()
+        {
+            Assert.Throws<ArgumentNullException>(() =>
+            {
+                this.DefaultFormatsManager.SetDecoder(null, new Mock<IImageDecoder>().Object);
+            });
+            Assert.Throws<ArgumentNullException>(() =>
+            {
+                this.DefaultFormatsManager.SetDecoder(ImageFormats.Bmp, null);
+            });
+            Assert.Throws<ArgumentNullException>(() =>
+            {
+                this.DefaultFormatsManager.SetDecoder(null, null);
+            });
+        }
+
+        [Fact]
+        public void RegisterMimeTypeEncoderReplacesLast()
+        {
+            IImageEncoder encoder1 = new Mock<IImageEncoder>().Object;
+            this.FormatsManagerEmpty.SetEncoder(TestFormat.GlobalTestFormat, encoder1);
+            IImageEncoder found = this.FormatsManagerEmpty.FindEncoder(TestFormat.GlobalTestFormat);
+            Assert.Equal(encoder1, found);
+
+            IImageEncoder encoder2 = new Mock<IImageEncoder>().Object;
+            this.FormatsManagerEmpty.SetEncoder(TestFormat.GlobalTestFormat, encoder2);
+            IImageEncoder found2 = this.FormatsManagerEmpty.FindEncoder(TestFormat.GlobalTestFormat);
+            Assert.Equal(encoder2, found2);
+            Assert.NotEqual(found, found2);
+        }
+
+        [Fact]
+        public void RegisterMimeTypeDecoderReplacesLast()
+        {
+            IImageDecoder decoder1 = new Mock<IImageDecoder>().Object;
+            this.FormatsManagerEmpty.SetDecoder(TestFormat.GlobalTestFormat, decoder1);
+            IImageDecoder found = this.FormatsManagerEmpty.FindDecoder(TestFormat.GlobalTestFormat);
+            Assert.Equal(decoder1, found);
+
+            IImageDecoder decoder2 = new Mock<IImageDecoder>().Object;
+            this.FormatsManagerEmpty.SetDecoder(TestFormat.GlobalTestFormat, decoder2);
+            IImageDecoder found2 = this.FormatsManagerEmpty.FindDecoder(TestFormat.GlobalTestFormat);
+            Assert.Equal(decoder2, found2);
+            Assert.NotEqual(found, found2);
+        }        
+
+        [Fact]
+        public void AddFormatCallsConfig()
+        {
+            var provider = new Mock<IConfigurationModule>();
+            var config = new Configuration();
+            config.Configure(provider.Object);
+
+            provider.Verify(x => x.Configure(config));
+        }
+    }
+}