There are lots of things to test besides basic aerodynamics. And even for that sometimes you want real data to validate models before building the full size thing.
Things that are tested/validated in wind tunnels nowadays: effect of different paint and coatings, engine inlet flow, noise, tunned mass dampers, effect of placement of sensors, control surface flutter.
Things that are tested/validated in wind tunnels nowadays: effect of different paint and coatings, engine inlet flow, noise, tunned mass dampers, effect of placement of sensors, control surface flutter.