Index: Core/Components/src/Core.Components.GraphSharp.Forms/Converters/PointedTreeVertexTypeToStringConverter.cs
===================================================================
diff -u -r6189fae3f21e2ee5eac80441472c2bcd5124c3da -r7824b1299ee61690e6bbbb5e665c80e516813653
--- Core/Components/src/Core.Components.GraphSharp.Forms/Converters/PointedTreeVertexTypeToStringConverter.cs	(.../PointedTreeVertexTypeToStringConverter.cs)	(revision 6189fae3f21e2ee5eac80441472c2bcd5124c3da)
+++ Core/Components/src/Core.Components.GraphSharp.Forms/Converters/PointedTreeVertexTypeToStringConverter.cs	(.../PointedTreeVertexTypeToStringConverter.cs)	(revision 7824b1299ee61690e6bbbb5e665c80e516813653)
@@ -34,7 +34,7 @@
     {
         public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
         {
-            if (targetType != typeof(string) || value == null)
+            if (value == null)
             {
                 return null;
             }
@@ -46,7 +46,9 @@
                 case PointedTreeVertexType.Diamond:
                     return "Diamond";
                 default:
-                    throw new InvalidEnumArgumentException();
+                    throw new InvalidEnumArgumentException(nameof(value),
+                                                           (int) value,
+                                                           typeof(PointedTreeVertexType));
             }
         }
 
Index: Core/Components/src/Core.Components.GraphSharp.Forms/Core.Components.GraphSharp.Forms.csproj
===================================================================
diff -u -r6189fae3f21e2ee5eac80441472c2bcd5124c3da -r7824b1299ee61690e6bbbb5e665c80e516813653
--- Core/Components/src/Core.Components.GraphSharp.Forms/Core.Components.GraphSharp.Forms.csproj	(.../Core.Components.GraphSharp.Forms.csproj)	(revision 6189fae3f21e2ee5eac80441472c2bcd5124c3da)
+++ Core/Components/src/Core.Components.GraphSharp.Forms/Core.Components.GraphSharp.Forms.csproj	(.../Core.Components.GraphSharp.Forms.csproj)	(revision 7824b1299ee61690e6bbbb5e665c80e516813653)
@@ -101,6 +101,11 @@
     <None Include="packages.config" />
   </ItemGroup>
   <ItemGroup>
+    <ProjectReference Include="..\..\..\Common\src\Core.Common.Utils\Core.Common.Utils.csproj">
+      <Project>{F49BD8B2-332A-4C91-A196-8CCE0A2C7D98}</Project>
+      <Name>Core.Common.Utils</Name>
+      <Private>False</Private>
+    </ProjectReference>
     <ProjectReference Include="..\Core.Components.GraphSharp\Core.Components.GraphSharp.csproj">
       <Project>{32358941-77c5-48a7-ad8b-dfb4f23b12a5}</Project>
       <Name>Core.Components.GraphSharp</Name>
Index: Core/Components/test/Core.Components.GraphSharp.Forms.Test/Converters/PointedTreeVertexTypeToStringConverterTest.cs
===================================================================
diff -u -r6189fae3f21e2ee5eac80441472c2bcd5124c3da -r7824b1299ee61690e6bbbb5e665c80e516813653
--- Core/Components/test/Core.Components.GraphSharp.Forms.Test/Converters/PointedTreeVertexTypeToStringConverterTest.cs	(.../PointedTreeVertexTypeToStringConverterTest.cs)	(revision 6189fae3f21e2ee5eac80441472c2bcd5124c3da)
+++ Core/Components/test/Core.Components.GraphSharp.Forms.Test/Converters/PointedTreeVertexTypeToStringConverterTest.cs	(.../PointedTreeVertexTypeToStringConverterTest.cs)	(revision 7824b1299ee61690e6bbbb5e665c80e516813653)
@@ -20,8 +20,10 @@
 // All rights reserved.
 
 using System;
+using System.ComponentModel;
 using System.Globalization;
 using System.Windows.Data;
+using Core.Common.TestUtil;
 using Core.Components.GraphSharp.Data;
 using Core.Components.GraphSharp.Forms.Converters;
 using NUnit.Framework;
@@ -55,16 +57,17 @@
         }
 
         [Test]
-        public void Convert_TargetTypeNotString_ReturnNull()
+        public void Convert_InvalidPointedTreeVertexType_ThrowsInvalidEnumArgumentException()
         {
             // Setup
             var converter = new PointedTreeVertexTypeToStringConverter();
 
             // Call
-            object convertedValue = converter.Convert(string.Empty, typeof(object), null, CultureInfo.InvariantCulture);
+            TestDelegate test = () => converter.Convert((PointedTreeVertexType) 99, typeof(string), null, CultureInfo.InvariantCulture);
 
             // Assert
-            Assert.IsNull(convertedValue);
+            const string message = "The value of argument 'value' (99) is invalid for Enum type 'PointedTreeVertexType'.";
+            TestHelper.AssertThrowsArgumentExceptionAndTestMessage<InvalidEnumArgumentException>(test, message);
         }
 
         [Test]
Index: Core/Components/test/Core.Components.GraphSharp.Forms.Test/Core.Components.GraphSharp.Forms.Test.csproj
===================================================================
diff -u -r6189fae3f21e2ee5eac80441472c2bcd5124c3da -r7824b1299ee61690e6bbbb5e665c80e516813653
--- Core/Components/test/Core.Components.GraphSharp.Forms.Test/Core.Components.GraphSharp.Forms.Test.csproj	(.../Core.Components.GraphSharp.Forms.Test.csproj)	(revision 6189fae3f21e2ee5eac80441472c2bcd5124c3da)
+++ Core/Components/test/Core.Components.GraphSharp.Forms.Test/Core.Components.GraphSharp.Forms.Test.csproj	(.../Core.Components.GraphSharp.Forms.Test.csproj)	(revision 7824b1299ee61690e6bbbb5e665c80e516813653)
@@ -96,6 +96,10 @@
     <None Include="packages.config" />
   </ItemGroup>
   <ItemGroup>
+    <ProjectReference Include="..\..\..\Common\test\Core.Common.TestUtil\Core.Common.TestUtil.csproj">
+      <Project>{D749EE4C-CE50-4C17-BF01-9A953028C126}</Project>
+      <Name>Core.Common.TestUtil</Name>
+    </ProjectReference>
     <ProjectReference Include="..\..\src\Core.Components.GraphSharp.Forms\Core.Components.GraphSharp.Forms.csproj">
       <Project>{4e575459-ad64-4f5f-b313-9f8e0ec8c03f}</Project>
       <Name>Core.Components.GraphSharp.Forms</Name>