The same could be said for any of the movable control surfaces, e.g. the flaps, ailerons, landing gear, rudder etc. The answer being that these things are test

The same could be said for any of the movable control surfaces, e.g. the flaps, ailerons, landing gear, rudder etc. The answer being that these things are tested to destruction and procedures and failsafes put in place when necessary. Edit: For the wingtips specifically I'd imagine not a lot of difference at all control-wise, just a loss of efficiency.