All units are tested under MultiWii Config to verify that all sensors work and produce sensible results. All the following systems are tested before shipping: PowerOn Test (HiPOT), USB connection, Atmel ATMega328P, Gyro, Acc, Mag & Baro. This is a working test of all electrical circuits. A regular number of units are also flight tested to maintain quality control. Also, all warranty units are flight tested before return shipping.