Almost no one does a dry pressure test. Typically people will run the pump on a separate power supply with the main system powered off, put paper towels underneath the connections, and let it run for a day and see if there are any leaks.
The maximum pressure put out by a 355 pump is about 8 PSI. Two of those can do 16 PSI, and that's the highest pressure you will ever see in a system. A CO2 cartridge is 853 PSI... I would say you are running a high risk of damaging something by using one. Just do the one day leakage test.
As others have said, this is a quick way to damage a loop.
I've seen people do the blow test, where they'll blow into a hose attached to the loop and see if it holds pressure against their lungs. Probably good enough to see if you left any fittings loose or disconnected, but not likely to find pinhole leaks due to a cut o-ring or the like.
I tried to nitrogen test a radiator to less than 100psi.(was considering using for 134a to make a phase change loop) and it blew the rad up like a balloon. All the copper and fins swelled...so yea, don't do that. Lol
Any reasonable positive pressure to do any real dry testing will be too much or you need some real good equipment to measure very small pressure decay off say 20psi or so.