diff --git a/src/Umbraco.Core/PluginTypeResolver.cs b/src/Umbraco.Core/PluginTypeResolver.cs
index d2e373fdd5..be16fc6ff3 100644
--- a/src/Umbraco.Core/PluginTypeResolver.cs
+++ b/src/Umbraco.Core/PluginTypeResolver.cs
@@ -2,6 +2,7 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
+using System.Reflection;
 using System.Text;
 using System.Threading;
 
@@ -49,6 +50,17 @@ namespace Umbraco.Core
 		internal readonly TypeFinder2 TypeFinder = new TypeFinder2();
 		private readonly ReaderWriterLockSlim _lock = new ReaderWriterLockSlim();
 		private readonly HashSet<TypeList> _types = new HashSet<TypeList>();
+		private IEnumerable<Assembly> _assemblies;
+
+		/// <summary>
+		/// Gets/sets which assemblies to scan when type finding, generally used for unit testing, if not explicitly set
+		/// this will search all assemblies known to have plugins and exclude ones known to not have them.
+		/// </summary>
+		internal IEnumerable<Assembly> AssembliesToScan
+		{
+			get { return _assemblies ?? (_assemblies = TypeFinder2.GetAssembliesWithKnownExclusions()); }
+			set { _assemblies = value; }
+		}
 
 		/// <summary>
 		/// Used to create instances of the specified type based on the resolved/cached plugin types
@@ -107,7 +119,7 @@ namespace Umbraco.Core
 		/// <returns></returns>
 		internal IEnumerable<Type> ResolveTypes<T>()
 		{
-			return ResolveTypes<T>(() => TypeFinder.FindClassesOfType<T>());
+			return ResolveTypes<T>(() => TypeFinder.FindClassesOfType<T>(AssembliesToScan));
 		}
 
 		/// <summary>
@@ -119,7 +131,7 @@ namespace Umbraco.Core
 		internal IEnumerable<Type> ResolveTypesWithAttribute<T, TAttribute>()
 			where TAttribute : Attribute
 		{
-			return ResolveTypes<T>(() => TypeFinder.FindClassesOfTypeWithAttribute<T, TAttribute>());
+			return ResolveTypes<T>(() => TypeFinder.FindClassesOfTypeWithAttribute<T, TAttribute>(AssembliesToScan));
 		}
 
 		/// <summary>
diff --git a/src/Umbraco.Tests/PluginTypeResolverTests.cs b/src/Umbraco.Tests/PluginTypeResolverTests.cs
index b9538191b7..b5428e42e7 100644
--- a/src/Umbraco.Tests/PluginTypeResolverTests.cs
+++ b/src/Umbraco.Tests/PluginTypeResolverTests.cs
@@ -1,12 +1,47 @@
 using System.Linq;
 using NUnit.Framework;
+using SqlCE4Umbraco;
 using Umbraco.Core;
+using Umbraco.Web;
+using umbraco.DataLayer;
+using umbraco.MacroEngines;
+using umbraco.MacroEngines.Iron;
+using umbraco.businesslogic;
+using umbraco.cms.businesslogic;
+using umbraco.uicontrols;
 
 namespace Umbraco.Tests
 {
 	public class PluginTypeResolverTests
 	{
 
+		[SetUp]
+		public void Initialize()
+		{
+			//for testing, we'll specify which assemblies are scanned for the PluginTypeResolver
+			PluginTypeResolver.Current.AssembliesToScan = new[]
+			    {
+			        this.GetType().Assembly, 
+			        typeof(ApplicationStartupHandler).Assembly,
+			        typeof(SqlCEHelper).Assembly,
+			        typeof(CMSNode).Assembly,
+			        typeof(System.Guid).Assembly,
+			        typeof(NUnit.Framework.Assert).Assembly,
+			        typeof(Microsoft.CSharp.CSharpCodeProvider).Assembly,
+			        typeof(System.Xml.NameTable).Assembly,
+			        typeof(System.Configuration.GenericEnumConverter).Assembly,
+			        typeof(System.Web.SiteMap).Assembly,
+			        typeof(TabPage).Assembly,
+			        typeof(System.Web.Mvc.ActionResult).Assembly,
+			        typeof(TypeFinder2).Assembly,
+			        typeof(ISqlHelper).Assembly,
+			        typeof(DLRScriptingEngine).Assembly,
+			        typeof(ICultureDictionary).Assembly,
+					typeof(UmbracoContext).Assembly
+
+			    };
+		}
+
 		[Test]
 		public void Ensure_Only_One_Type_List_Created()
 		{
@@ -22,6 +57,20 @@ namespace Umbraco.Tests
 			Assert.AreEqual(2, foundTypes1.Count());
 		}
 
+		[Test]
+		public void Resolves_Trees()
+		{
+			var trees = PluginTypeResolver.Current.ResolveTrees();
+			Assert.AreEqual(26, trees.Count());
+		}
+
+		[Test]
+		public void Resolves_Applications()
+		{
+			var apps = PluginTypeResolver.Current.ResolveApplications();
+			Assert.AreEqual(7, apps.Count());
+		}
+
 		public interface IFindMe
 		{
 
diff --git a/src/Umbraco.Tests/TypeFinderBenchmarkTests.cs b/src/Umbraco.Tests/TypeFinderBenchmarkTests.cs
index 97954bcb85..2c61502a78 100644
--- a/src/Umbraco.Tests/TypeFinderBenchmarkTests.cs
+++ b/src/Umbraco.Tests/TypeFinderBenchmarkTests.cs
@@ -36,9 +36,7 @@ namespace Umbraco.Tests
 		{
 			_assemblies = new[]
 			    {
-			        //both contain the type
 			        this.GetType().Assembly, 
-			        //these dont contain the type
 			        typeof(ApplicationStartupHandler).Assembly,
 			        typeof(SqlCEHelper).Assembly,
 			        typeof(CMSNode).Assembly,
diff --git a/src/umbraco.businesslogic/ApplicationRegistrar.cs b/src/umbraco.businesslogic/ApplicationRegistrar.cs
index 47139638f3..29cd59ba37 100644
--- a/src/umbraco.businesslogic/ApplicationRegistrar.cs
+++ b/src/umbraco.businesslogic/ApplicationRegistrar.cs
@@ -32,8 +32,10 @@ namespace umbraco.BusinessLogic
             // Load all Applications by attribute and add them to the XML config
         	var types = PluginTypeResolver.Current.ResolveApplications();
 
-			//we can have multiple attributes so we'll query for them
-            var attrs = types.Select(x => (ApplicationAttribute)x.GetCustomAttributes(typeof(ApplicationAttribute), false).Single())
+			//since applications don't populate their metadata from the attribute and because it is an interface, 
+			//we need to interrogate the attributes for the data. Would be better to have a base class that contains 
+			//metadata populated by the attribute. Oh well i guess.
+			var attrs = types.Select(x => x.GetCustomAttributes<ApplicationAttribute>(false).Single())
                 .Where(x => Application.getByAlias(x.Alias) == null);
 
             var allAliases = Application.getAll().Select(x => x.alias).Concat(attrs.Select(x => x.Alias));
diff --git a/src/umbraco.businesslogic/ApplicationTreeRegistrar.cs b/src/umbraco.businesslogic/ApplicationTreeRegistrar.cs
index 2a9cd706d0..5ba139a3ff 100644
--- a/src/umbraco.businesslogic/ApplicationTreeRegistrar.cs
+++ b/src/umbraco.businesslogic/ApplicationTreeRegistrar.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Linq;
 using System.Xml.Linq;
+using Umbraco.Core;
 using umbraco.BusinessLogic.Utils;
 using umbraco.DataLayer;
 using umbraco.businesslogic;
@@ -29,14 +30,13 @@ namespace umbraco.BusinessLogic
 
         public ApplicationTreeRegistrar()
         {
-            // Load all Applications by attribute and add them to the XML config
-			var typeFinder = new Umbraco.Core.TypeFinder2();
-			var types = typeFinder.FindClassesOfType<ITree>()
-                .Where(x => x.GetCustomAttributes(typeof(TreeAttribute), false).Any());
+            // Load all Trees by attribute and add them to the XML config
+			var types = PluginTypeResolver.Current.ResolveTrees();
 
-            var items = types.Select(x => new Tuple<Type, TreeAttribute>(x,
-                                                                         (TreeAttribute)x.GetCustomAttributes(typeof(TreeAttribute), false).Single()))
-                .Where(x => ApplicationTree.getByAlias(x.Item2.Alias) == null);
+        	var items = types
+        		.Select(x =>
+        		        new Tuple<Type, TreeAttribute>(x, x.GetCustomAttributes<TreeAttribute>(false).Single()))
+        		.Where(x => ApplicationTree.getByAlias(x.Item2.Alias) == null);
 
             var allAliases = ApplicationTree.getAll().Select(x => x.Alias).Concat(items.Select(x => x.Item2.Alias));
             var inString = "'" + string.Join("','", allAliases) + "'";
diff --git a/src/umbraco.businesslogic/PluginTypeResolverExtensions.cs b/src/umbraco.businesslogic/PluginTypeResolverExtensions.cs
index f3acbfd55e..724ad770ba 100644
--- a/src/umbraco.businesslogic/PluginTypeResolverExtensions.cs
+++ b/src/umbraco.businesslogic/PluginTypeResolverExtensions.cs
@@ -21,7 +21,7 @@ namespace umbraco.businesslogic
 		}
 
 		/// <summary>
-		/// Returns all available IApplication object
+		/// Returns all available IApplication in application
 		/// </summary>
 		/// <param name="resolver"></param>
 		/// <returns></returns>
@@ -30,5 +30,15 @@ namespace umbraco.businesslogic
 			return resolver.ResolveTypesWithAttribute<IApplication, ApplicationAttribute>();
 		}
 
+		/// <summary>
+		/// Returns all available ITrees in application
+		/// </summary>
+		/// <param name="resolver"></param>
+		/// <returns></returns>
+		internal static IEnumerable<Type> ResolveTrees(this PluginTypeResolver resolver)
+		{
+			return resolver.ResolveTypesWithAttribute<ITree, TreeAttribute>();
+		}
+
 	}
 }
\ No newline at end of file