Ok, I took my PSU to the PC shop, and they said they could help me out for free.
First, he hooked up the main power cable of the PSU to his own PC motherboard, and the power cable on the opposite end of the PSU, then he just booted up his PC. The he showed me the readings, saying there's nothing wrong with it.
I asked him if he could do more in-depth tests. He said it would take a few hours. So I left the PSU with him, and came back a few hours later.
When I asked him what was the results, he said there was nothing wrong with it. I asked him what kind of test did he do, he said he hooked it up to a PC, surfed the internet a bit, and it didn't shut down or anything.
I do believe him when he said there was nothing wrong with it, but only because I don't believe he really tested the PSU properly, as in he didn't use multimeters or any form of measuring device. I believe he came to the conclusion simply by hooking it up to his PC. Whether or not if he did push the PSU to its limit, that I'm not sure of.
What do I make of this result?