See, the thing is... volume is generally not the issue. If you hook a pump up to an injector or multiple and rotate the pump by hand(or with a drill), you can see if it'll squirt fuel.
The things that practically matter for a working pump are:
1. Cranking volume/pressure(can it create enough pressure to inject at cranking speeds). This can be checked with a drill/motor hooked up to the pump on a DIY bench.
2. Heat soak(which is cranking volume/pressure with the pump at high temps). Not sure on how to test that on a bench, and I'm guessing it's hard to test with a proper stand... which is why that's a major complaint with cheap rebuilds.
3. Injection timing. This is arguably one of the most important factors for a street pump, and one thats pretty hard to measure without a fairly in depth stand setup. You'd need at least a magnet and pickup on the drive gear, and a piezo pickup on an injector line, plus device for measuring time/degrees between the two pulses.