A vehicle safety system testing method provides an indication of how the safety system responds during a crash event while the system is exposed to electromagnetic energy. The system is exposed to electromagnetic energy to obtain EMI data indicating the system performance under those conditions. Separate crash data indicating the system response to a crash event is obtained using computer simulation or known test equipment. The EMI data is superimposed onto the crash data to provide an indication of how the system performs when exposed to both conditions. In one example, the EMI data is superimposed onto the crash data and the resulting data is provided to the system controller so that the controller response can be determined. In one example, the ability of the system to accurately issue deploy commands to an airbag squib is tested at selected EMI frequencies.