- don't try to mock impls

LightweightIocContainer.Validation/IocValidator.cs

@@ -90,6 +90,9 @@ public class IocValidator
         if (type == typeof(string))
             return string.Empty;
 
+        if (type.IsInterface)
+            return new NullParameter(type);
+            
         try
         {
             return GenericMethodCaller.CallPrivate(this, nameof(GetMock), type);