Boost unit test: adding a helper method or private function

I have a BOOST_AUTO_TEST_CASE which needs a helper function. I could just make this a regular function and call it from within; but I'd rather somehow keep it local and private to the scope of the BOOST_AUTO_CASE. I'd also like to be able to declare vars which are in the scope of both the test case and the helper functions (e.g. const int serverCount = 10;).

If the test case was a class (and not a macro), I'd simply use a private member function. How do I do this (or the equivalent) for a Boost unit test case?