Error: 'this' is only defined in non-static member functions

[A Guy With a Question]

I have an interface where I have a classes embedded in it's scope 
(trying to create something for the classes that implement the 
interface can use for unittesting).

     interface IExample
     {
         // stuff ...
         class Tester
         {

         }
     }

I'm trying to make an instance of it like:

     auto tester = new IExample.Tester();

And I get the above error.