Pulling a single code unit out to test is fine so long as interrupts and other race conditions are not involved, but you must do end-to-end system tests regardl

Pulling a single code unit out to test is fine so long as interrupts and other race conditions are not involved, but you must do end-to-end system tests regardless and with extremes of voltage and temperature, corrupted IO etc. It's also good to also test your device without watchdog timers, BOR, stack overflow resets enabled to catch anything that will normally fix itself. By the way I recommend all the BOR/Watchdog timers and bit error/stack overflow errors to POR the chip if it has the option, I still see commercial controllers and devices locking up and needing a manual power off reset, really unprofessional, so totally enable all these if your micro has them.