Disclosed herein is a test circuit for a device under test. The test circuit includes a scan chain configured to receive test pattern data and to shift the test pattern data to the device under test, and being clocked by a reference clock, and a clock circuit configured to operate in either a clock generation mode or a frequency determination mode. The clock circuit, when in the clock generation mode and when the test circuit is in a normal mode of operation, is configured to pass a first clock signal to the device under test. The clock circuit, when in the clock generation mode and when the test circuit is in a test mode of operation, is configured to pass the reference clock to the device under test. The clock circuit, when in the frequency determination mode, counts a frequency of the first clock signal.