Fixes tests

src/Umbraco.Core/Udi.cs

@@ -58,6 +58,9 @@ namespace Umbraco.Core
                     if (fi.IsLiteral && fi.IsInitOnly == false)
                     {
                         var udiType = fi.GetCustomAttribute<Constants.UdiTypeAttribute>();
+
+                        if (udiType == null) 
+                            throw new InvalidOperationException("All Constants listed in UdiEntityType must be attributed with " + typeof(Constants.UdiTypeAttribute));
                         result[fi.GetValue(null).ToString()] = udiType.UdiType;
                     }                        
                 }

src/Umbraco.Core/UdiEntityType.cs

@@ -55,10 +55,14 @@ namespace Umbraco.Core
 
             [UdiType(UdiType.GuidUdi)]
             public const string RelationType = "relation-type";
-            
+
             // forms
+
+            [UdiType(UdiType.GuidUdi)]
             public const string FormsForm = "forms-form";
+            [UdiType(UdiType.GuidUdi)]
             public const string FormsWorkflow = "forms-workflow";
+            [UdiType(UdiType.GuidUdi)]
             public const string FormsRecord = "forms-record";
 
             // string entity types