Dragon of SpaceX has been very successfully tested and used. But Dragon v2 seems to be differently designed and has 8 superdraco engines.

Has the v2 been drop tested from a balloon or helicopter? Have the 8 superdraco engines of the v2 been test fired together all at once in assembly, flying or on the ground? (Does SpaceX perform such major system tests out of public insight?)

It seems to me that a prototype of the Dragon v2, within a year, goes directly from a showroom exhibit to the first launch pad abort test in 50 years.