Disclosed is a test aid unit that is installed between automatic test equipment (ATE) and a device under test (DUT), generates a test data signal according to a data processing and transmission/reception rate of the DUT in response to a control signal transmitted from the ATE, transmits the test data signal to the DUT, self-tests a test result signal transmitted from the DUT, and transmits the test result to the ATE. The test aid unit includes a clock signal divider, an integrated digital logic unit, a transmitter, and a receiver.