Hardware and Loop Testing Can Work Very Well and Be Worth It

First job out of university was in a hardware in the loop test lab for helicopter avionics. Workstations that would simulate all of the communication partners. So we'd have actual like, uh, flight control computers and then all of the radios,. All of the navigation gear was simulated in C code. But from the flight computer standpoint, it was just as if it was running in the real aircraft.