diff --git a/src/ProtocolBuffers.Test/CSharpOptionsTest.cs b/src/ProtocolBuffers.Test/CSharpOptionsTest.cs
new file mode 100644
index 0000000..d22f99d
--- /dev/null
+++ b/src/ProtocolBuffers.Test/CSharpOptionsTest.cs
@@ -0,0 +1,70 @@
+﻿using Google.ProtocolBuffers.DescriptorProtos;
+using Google.ProtocolBuffers.Descriptors;
+using NUnit.Framework;
+
+namespace Google.ProtocolBuffers {
+  [TestFixture]
+  public class DescriptorUtilTest {
+    [Test]
+    public void ExplicitNamespace() {
+      FileDescriptorProto proto = new FileDescriptorProto.Builder {
+        Name = "x", Package = "pack", Options = new FileOptions.Builder().SetExtension(CSharpOptions.CSharpFileOptions,
+          new CSharpFileOptions.Builder { Namespace = "Foo.Bar" }.Build()).Build()
+      }.Build();
+      FileDescriptor descriptor = FileDescriptor.BuildFrom(proto, null);
+      Assert.AreEqual("Foo.Bar", descriptor.CSharpOptions.Namespace);
+    }
+
+    [Test]
+    public void NoNamespaceFallsBackToPackage() {
+      FileDescriptorProto proto = new FileDescriptorProto.Builder { Name = "x", Package = "pack" }.Build();
+      FileDescriptor descriptor = FileDescriptor.BuildFrom(proto, null);
+      Assert.AreEqual("pack", descriptor.CSharpOptions.Namespace);
+    }
+
+    [Test]
+    public void NoNamespaceOrPackageFallsBackToEmptyString() {
+      FileDescriptorProto proto = new FileDescriptorProto.Builder { Name = "x" }.Build();
+      FileDescriptor descriptor = FileDescriptor.BuildFrom(proto, null);
+      Assert.AreEqual("", descriptor.CSharpOptions.Namespace);
+    }
+
+    [Test]
+    public void ExplicitlyNamedFileClass() {
+      FileDescriptorProto proto = new FileDescriptorProto.Builder {
+        Name = "x", Options = new FileOptions.Builder().SetExtension(CSharpOptions.CSharpFileOptions,
+          new CSharpFileOptions.Builder { UmbrellaClassname = "Foo" }.Build()).Build()
+      }.Build();
+      FileDescriptor descriptor = FileDescriptor.BuildFrom(proto, null);
+      Assert.AreEqual("Foo", descriptor.CSharpOptions.UmbrellaClassname);
+    }
+
+    [Test]
+    public void ImplicitFileClassWithProtoSuffix() {
+      FileDescriptorProto proto = new FileDescriptorProto.Builder { Name = "foo_bar.proto" }.Build();
+      FileDescriptor descriptor = FileDescriptor.BuildFrom(proto, null);
+      Assert.AreEqual("FooBar", descriptor.CSharpOptions.UmbrellaClassname);
+    }
+
+    [Test]
+    public void ImplicitFileClassWithProtoDevelSuffix() {
+      FileDescriptorProto proto = new FileDescriptorProto.Builder { Name = "foo_bar.protodevel" }.Build();
+      FileDescriptor descriptor = FileDescriptor.BuildFrom(proto, null);
+      Assert.AreEqual("FooBar", descriptor.CSharpOptions.UmbrellaClassname);
+    }
+
+    [Test]
+    public void ImplicitFileClassWithNoSuffix() {
+      FileDescriptorProto proto = new FileDescriptorProto.Builder { Name = "foo_bar" }.Build();
+      FileDescriptor descriptor = FileDescriptor.BuildFrom(proto, null);
+      Assert.AreEqual("FooBar", descriptor.CSharpOptions.UmbrellaClassname);
+    }
+
+    [Test]
+    public void ImplicitFileClassWithDirectoryStructure() {
+      FileDescriptorProto proto = new FileDescriptorProto.Builder { Name = "x/y/foo_bar" }.Build();
+      FileDescriptor descriptor = FileDescriptor.BuildFrom(proto, null);
+      Assert.AreEqual("FooBar", descriptor.CSharpOptions.UmbrellaClassname);
+    }
+  }
+}