No flight test for the ATPL, -273, but of course the regular checks to keep the type rating current should be perfectly adequate, and I would still say that 500 hours multi-crew (in effect much more as I believe P2 hours only count for half, so only P1(S) counts fully) would be much more important than a flight test or any number of hours flying puddle jumpers. I have known an FAA ATPL holder with a lot of hours on his own aircraft who went to command a multi-crew aircraft with little idea of what he was doing in that environment.
I have learnt a lot as an instructor, and it will make me a great First Officer. It did not give me the skills to be a good Captain of a complicated, multi-crew aircraft yet, just a good basis for then. Why should I be given the privilege of commanding a large, complicated aircraft on my licence (the only difference between an ATPL and a CPL/IR) on the strength of flying a Robin, a 152 and a Cherokee?