Advanced Driver-Assistance Systems (ADASs) have become increasingly popular. To ensure safety, simulation testing is essential. In this research, we conducted a case study to investigate the fault-detection effectiveness of existing ADAS testing standards: We tested the Lane Keeping Assist System (LKAS), which is a prebuilt ADAS module of MATLAB and Simulink. We first tested LKAS using the European New Car Assessment Programme (Euro NCAP), which contains 40 prebuilt driving scenarios in MATLAB. Our results show that none of the 40 scenarios detected any failure. We then continued the tests by applying a simple metamorphic relation equivalence under geometric transformation, and a previously unknown real-life bug in LKAS was immediately revealed. We reported this finding to the MATLAB team in the US, who then confirmed the bug and corrected the LKAS code. This research provides a strong case for incorporating metamorphic testing into ADAS testing standards and protocols.