Safety, availability, and cost considerations can make performing thorough tests of embedded control devices using the complete system impractical. Hardware-in-the-loop (HIL) simulation is a real-time test technique used to test these devices more efficiently. During HIL test, the physical system that interfaces to an embedded control device is simulated on real-time hardware, and the outputs of the simulator mimic the actual output of the physical system. The embedded controller “thinks” it is in a real system. HIL simulation meticulously tests embedded control devices in a virtual environment before proceeding to real-world tests of the complete system. This application note covers recommended best practices for powertrain HIL testing.