Welcome to the Susquehanna Rowing Association!
In a flip test is you flip your boat on purpose. The flip test prepares you to get back into the boat if you flip by accident. No one flips on purpose. It can happen to even experienced rowers. It can happen because of winds, chop, an imbalance between your weight and the boat’s weight class, your power and other causes. Here's a video what to expect:
http://www.row2k.com/video/Sculling-flip-test-demonstration/7708/
The club hosts this flip test once each year.