HIL (hardware in the loop) and SIL (software in the loop) are two kinds of methodology of testing, applied in the development of advanced engineering systems such as car and air systems.

HIL tests rely on testing physical objects (ex. motor, gearbox, or steering systems) by connecting them to simulated models of the rest of the system. The model generates signals which imitate real values allowing us to test components before installing them.

SIL tests are tests which rate software functionality without the need to use physical objects. In this type of testing the program is run in a test environment which delivers simulations of real input values and examines the effectiveness of the software’s answers.