I installed my cpu and motherboard, connected It to the psu and turned it on to see if it got power. All I got was a quick flash on the motherboards rgb light and it turned off.
Like said, a LED, debug code can light up, hard drives will spin up, fans too, optical drive can open and close. But this won't tell you anything about a correctly working motherboard, CPU or power supply. At least RAM, CPU with cooler, motherboard and a Psu is necessary
Most will beep/display a code if no display adapter is present (if applicable); but, the act of getting teh code tells you the board and CPU are at least somewhat working...
Like said, a LED, debug code can light up, hard drives will spin up, fans too, optical drive can open and close. But this won't tell you anything about a correctly working motherboard, CPU or power supply. At least RAM, CPU with cooler, motherboard and a Psu is necessary