Wasted enough time trying to find my power supply tester so I ended up buying one.
I got the Kingwin KPST-01 power supply tester
Not much documentation, but I will try to add some.
Normally you would plug this in before turning it on, the right side has the main motherboard connector. Note on the left side there is a smaller connector, if you do not connect the left side, the 12V2 rail will blink L.L and you will have a warning beep sound.
The others give off the 5V 3.3V and 12V, this coolmaster power supply is showing slightly less than 12V and slightly more than 5V.
The 280ms PG measures how long before the power supply sends a “Power Good” signal to the motherboard, it should be between 100 and 500ms
The bottom port (which you can barely see in this picture) measure the old school HD power molex and the 12v and 5v LED on the left should turn on.
The top port (which you cannot see) measures a SATA power connector and should light up all three 12V 3.3V and 5V.
The left also has a floppy power connector and it too should only have 12V and 5V.
Finally on the left if you remove the 2nd 12V rail connector, you can test PCI-E power connectors.
Kind of cool, pain that there is not much documentation, but a little web research told me what I needed. Of course if I really wanted to test this I would test it on an o-scope.
Here are some external links that helped
https://www.lifewire.com/test-a-power-supply-using-a-power-supply-tester-2626160
https://www.passmark.com/support/lcd-power-supply-tester-faq.htm