A test assembly for testing an antenna-in-package (AiP) device (150) includes a socket (261) over a circuit board (270), where the socket includes an opening (260) for receiving the AiP device; a plunger (263) configured to move along sidewalls of the opening, where during testing of the AiP device, the plunger is configured to cause the AiP device to be pressed towards the circuit board such that the AiP device is operatively coupled to the circuit board via input/output connections of the AiP device and of the circuit board; and a loadboard (250) disposed within the socket and between the plunger and the AiP device, where the loadboard includes a coupling structure configured to be electromagnetically coupled to a transmit antenna (143) and to a receive antenna (145) of the AiP device, so that testing signals transmitted by the transmit antenna are conveyed to the receive antenna externally relative to the AiP device through the coupling structure.