I can. I'm seeing automated tests. A whole lot of automated tests. Unit tests, performance tests, integration tests, executable specifications, tests with real hardware.

I can be done; you have to optimize for what's important to the project at hand.

People have been doing it with medical devices, so I don't think it's impossible. I agree it would have to be done differently, but then avionics waterfall has to be done differently than order-entry systems waterfall, so that's nothing new.