Working with unit tests and making a few corrections around ContentTypes.

src/Umbraco.Tests/CodeFirst/PluginManagerExtensions.cs

@@ -0,0 +1,17 @@
+using System;
+using System.Collections.Generic;
+using Umbraco.Core;
+
+namespace Umbraco.Tests.CodeFirst
+{
+    /// <summary>
+    /// Used for PluginTypeResolverTests
+    /// </summary>
+    internal static class PluginManagerExtensions
+    {
+        public static IEnumerable<Type> ResolveContentTypeBaseTypes(this PluginManager resolver)
+        {
+            return resolver.ResolveTypes<ContentTypeBase>();
+        }
+    }
+}