In the Portal 2 Perpetual Testing Initiative (the map builder) you can test out your maps by going to the Game View. If you're building a co-op map, the Game View is automatically split screen, each controlled by one robot. How do I switch control of robots to test my map? Currently I can only control Atlas, but I need to switch over to P-body to complete the map. He's just sitting there, stuck at the beginning of the level.
I've tried using gestures, pinging, and keyboard shortcuts, but nothing has worked so far.