First, welcome to the M2M world!
I've been responsible for certifying M2M devices for Jasper for the last 4.5 years, so I have little experience in this area. The key testing component from the operator's perspective is ensuring the device doesn't cause harm to the network. M2M device applications are notorious for having retry algorithms that can cause havic. I recommend testing the items listed in the generic retry algorigthm from this document http://m2m.com/docs/DOC-1007.