The present invention discloses a test device for testing an integrated circuit. An embodiment of the test device includes an on-chip-clock controller (OCC), a pulse debugging circuit and a register circuit. The OCC is configured to generate an output clock according to an input clock, in which the output clock is for testing a circuitry under test (CUT) that is included in the test device. The pulse debugging circuit is configured to generate a pulse record according to a pulse number of the output clock, in which the pulse record is used to find out whether a test status dependent upon the output clock is abnormal. The register circuit is configured to store and output the pulse record according to a reliable clock.