In a method for testing integrity of signals transmitted from hard disk interfaces using a computing device, the computing device connects to an oscilloscope and a mechanical arm that is equipped with a test fixture. The mechanical arm controls the test fixture to make contact with one of the hard disk interfaces to be tested. The method adjusts an intensity grade of the signals through the hard disk interface, and controls the hard disk interface to produce a signal corresponding to the adjusted intensity grade. The test fixture obtains the signal from the hard disk interface, and the oscilloscope measures one or more test parameters of the signal. The method analyzes values of the test parameters to find an optimal signal, determines an intensity grade of the optimal signal as a driving parameter of the hard disk interface, and generates a test report of the hard disk interfaces.