The invention relates to a tester apparatus of the kind including a portable supporting structure for removably holding and testing a substrate carrying a microelectronic circuit. An interface on the stationary structure is connected to the first interface when the portable structure is held by the stationary structure and is disconnected from the first interface when the portable supporting structure is removed from the stationary structure. An electrical tester is connected through the interfaces so that signals may be transmitted between the electrical tester and the microelectronic circuit to test the microelectronic circuit.