How to register extended unit test attribute for Visual Studio 2013 Professional

I'm trying to extend MS unit test class in Visual Studio 2013, in accordance with the guideline below.

Extending the Visual Studio Unit Test Type, part 1

But it does not works fine.

With my .pdb and .dll files copying to PrivateAssemblies folder under the VS installed directory, VS steps into extended TestClassAttribute to find ExtentionID, but the test method failed with the errormessage telling failed to initialize the unit test extension, as it is not registered .

I really carefully inspected the registry hierarchy and entry to match the guideline and found no error.(Although the upper node of VS version is different from 10.0 to 12.0)

I wonder if is it possible to extend unit class in my VS 2013 version "Professional" .

Also as far as I inspected, this issue is not so popular since VS 2013 was released.

Is extending unit test class is still effective in VS 2013?

I'll appreciate any hint, advice or solution.

Thanks.