Just make sure the fuel pump is turned off. Disconnect it, pull the fuse/relay or whatever it takes and then run your injector test. That’s how I did it with my Megasquirt. You should be able to hear the injectors click when they go high. If they don’t then you may have a short somewhere.
It’s a valid test but you should also test them for flow. They can click and not flow fuel. Running pressure to em and cycling them in to a bucket is a good idea.