The Wi-Fi Alliance, as usual, keep their interoperability test
procedures for Draft N under wrap.
As an aside I did find this web site which does have a pdf. of how they
did it for 11a,11b and 11g.

<http://www.iol.unh.edu/services/testing/wireless/testsuites/temp.html#802.11n%20Draft%202.0%20MAC%20STA%20Conf ormance%20Test%20Suite>