You can bench test.
But you will have to make up blanking plates to close up the inlet and outlet of the pump, in one of the blanking plates you will need a fitting to pump compressed air into the pump housing. No more than about 15 psi. I use fanstic house hold cleaner as a bubble test for leaks. Spray and watch for bubbles. Big bubbles a big leak, tiny foam a very small leak.
TonyK.
Grimsby Ontario Canada.