Abstract: A device for testing the logic states of integrated circuits while operating in-circuit. The device includes a hand-held housing containing a pair of spaced circuit boards to which a clip is electrically coupled, the clip having terminals for making electrical contact with the pins on a test IC. The device has a circuit programmed for a particular IC by a socket having removable pins of different lengths. The socket has means for receiving a reference IC against which the test IC is to be compared. Switch means coupled with the circuit permit individual testing of the pins of the test IC.