In the fourth generation (4G) communications, over-the-air (OTA) testing is mainly used for performance evaluation of long term evolution (LTE) user equipment (UE), because the characteristics of the internal antennas of the UE are generally unknown or not accessible. The 4G base station (BS), on the other hand, has well defined antenna ports. Hence, the BS antennas are usually measured separately, whereas the BS without antennas is usually evaluated by conductive testing. Popular 4G multiple-input multiple-output (MIMO) OTA testing methods for LTE UEs are multi-probe anechoic chamber (MPAC), radiated two-stage method (RTS), and reverberation chamber (RC). In the invited talk, we will compare the pros and cons of different OTA methods, with a special focus on their adaptability to OTA testing of 5G millimeter-wave (mmWave) and internet of things (IoT).