Is there a conceivable ground test that would meet the intent of this (i.e. not requiring actual flight test?)
I could postulate situations where I might want to do a ground test (eg a wind-tunnel test) to indicate the effect of something prior to undertaking flight tests. If the change is substantial enough to warrant wind-tunnel tests then my view is that subsequent flight test would be essential.
I can remember getting involved in the certification of an ultra-light aircraft here many years ago where the designer had done some ground tests for certification in another country. Towing the aeroplane tied down to a trailer behind his Porsche down a motorway at Vd instead of flight tests did not show conformance, in my opinion, to the specific requirements nor did it seem very smart to me. Well, it was smart in that it kept the risk low to the test pilot who didn't fly it above Vne but left future participants at risk.
I should note that I have been out of this business for a few years but thinking of getting involved again. Perhaps people do things differently here now (and differently from in the USA) and perhaps my comments are way off track.