Disclosed is a test system including a transmitter, a receiver, a measuring circuit, and a control circuit. The transmitter is coupled to the receiver in a DC coupling manner, and includes: a signal input circuit determining an output signal according to an input signal; a current source coupled between the signal input circuit and a low power-supply terminal and configured to determine a total current passing through the signal input circuit in a non-open/short-circuited condition; and a signal output wire circuit outputting the output signal for a performance test. The receiver includes: an impedance circuit coupled to the signal output wire circuit; and a coupling circuit coupling the impedance circuit with a high power-supply terminal. The measuring circuit measures a target current/voltage between the high power-supply terminal and low power-supply terminal to generate a measurement result. The control circuit determines whether the transmitter/receiver is open/short-circuited according to the measurement result.