"What the? Why won't my computer turn on? Crap! Did the power supply die?"
Pretty much anyone who has owned a computer has been in this situation. But sometimes there just isn't that handy spare power supply laying around to double check your suspicion. Thus it is always good knowledge knowing how to test a power supply. But how do you test a power supply? This seemingly magical act can actually be performed multiple ways.
One way it so simply buy a power supply tester online (as most computer gear stores don't carry them, at least in my neck of the woods). Most of them are very simple devices - plug in your main 20/24 pin power supply connector, make sure all the lights come up green and you're good to go. Coolmax has recently (to me anyway) released a very cool upgraded power supply tester - you plug in your main power connector as usual and it displays the voltages on an LCD screen for you.