A semiconductor test system includes a user device configured to operate a reference device in accordance with an interface signal based on a timing signal having a variable operating frequency, a pattern synthesis apparatus configured to measure an interval between adjacent edges of the timing signal transmitted from the user device, and extract a logic value of the interface signal in accordance with the timing signal so as to generate test pattern data, and a test device configured to receive the test pattern data, reconstruct the timing signal based on the measured interval, generate a test driving signal such that the logic value is extracted from a device under test (DUT) based on the reconstructed timing signal, and apply the test driving signal to the DUT so as to determine an operating state of the DUT.