While where at it discussing pop testers, just about any pop tester is OK as long as it will pump up to the desired pressure and not have any leaks.
To check an injector, pump it up to make it pop, adjust if needed to the 1850 or +, make it pop, record pop pressure, pump up second time to within 100#, hold for 10 seconds, if a fuel bubble appears and just hangs there for that amount of time it's a good one.
As precision ground the seat and plunger is a small leak (bubble) is of no consequence as fast as an injector in the engine running pops.
I don't pay much attention to the spray pattern, because an IDI sprays into the precup where it hits metal and disperses, unlike a DI engine where the spray pattern is of consequence, of course the finer dispersed spray the better it is. Everything happens in a matter of microseconds @ 1800 RPM.
Take notice, NO spark plugs.