visual studio 2010 - VS2010 and Create Unit Tests... no tests generated -

i'm trying add unit tests existing code base using visual studio 2010's unit test generator. however, in cases when open class, right click --> create unit tests..., after select methods generate tests create blank test. there situations can happen? in every case select @ least 1 public method gen tests for, , generates this:

using txrp.controllers; //the location of code tested using microsoft.visualstudio.testtools.unittesting; 

that's it. nothing else. strange, right?

i should note mvc 2 controller code, , have been able gen tests other controllers no problem, , controllers follow pretty same format. no error seems thrown, gens empty page happily , adds project if fine.

has had experience same type of thing happening, , there answer found why?

update: there in fact error during generation:

while trying generate tests, following errors occurred: value cannot null. parameter name: key 

after research, possible solution found error occurrs if you're trying generate tests test file exists. however, solution not working me...

if try generate tests class has existing tests in file in project, generate empty file described above. changing filename not sufficient, nor using different location within project. seems enforce one-testfile-per-class convention across entire project.