"I guess it works!" doesn't work for me either. It doesn't take that long to be sure. Most pistol problems are the ammo, extractor, magazine, or springs. The only failures I've ever had were a broken transfer bar on an LCR, and a broken trigger spring on a different LCR. So much for revolvers being more depedable, LOL......... if I experience a pistol malfunction my process is a little more thorough than to shoot one more round and declare "I guess it works!".
I'd need a bit more in order to feel confident I can defend myself from evil. Generally I'd like to see the gun run at least a box of FMJ and then perhaps a couple magazines of whatever I'm using for self defense without any more hiccups.
Suppose you replace a part? How much testing might that new part need before you're satisfied it's set to go? Are there any parts that you feel would need or warrant more thorough testing than others?
A new part or magazine get the same treatment. Two loadings with no problem, I'm happy.