Embodiments include a method and system for testing an electric circuit. A carrier signal of a first frequency is modulated with a multi-tone signal to generate a test signal. The test signal is applied to an input of a circuit under test (CUT). A crest factor of an output signal that corresponds to the test signal received at an output of the CUT is measured. A crest factor differential between the measured crest factor and a reference crest factor is determined. If the crest factor differential exceeds a threshold value, the CUT is determined to be defective.