The pilot of the Cessna reported that, he turned off the taxiway to perform a functional check of his autopilot and electric trim systems. A few seconds later, the pilot of a Kingair was taxiing and observed the Cessna’s tail partially obstructing the taxiway. The Kingair pilot turned sharply to the left to avoid an impact. As the Cessna pilot was checking his systems, he suddenly felt his airplane lurch forward. The Cessna pilot immediately observed the Kingair pass to his rear left and used the airport’s common traffic advisory frequency to inform the Kingair pilot that he had collided with his airplane. The Kingair pilot denied the ground collision and subsequently tookoff. As a result of the collision, the Cessna’s rudder and vertical stabilizer were substantially damaged. The right-wing winglet of the Kingair displayed minor red paint transfer. The pilots of both airplanes reported that there were no mechanical failures or malfunctions with their airplanes that would have precluded normal operation.