Put the ECU in the car, and start it. It's a DE ECU, so it's not going to run right, but it should at least tell you if the injector fires. Just don't run the car, leave it trying to idle. Pull the injector clip from #1 and see if you notice any change how the car runs.
Shouldn't take more than a minute to do.
If you don't want to do this, the only other way to test, would be to Ohm out the harness from the ECU plug to the injector harness plug. You'll need the FSM in order to check the right pin on the ECU side of the harness. You should have low~no resistance. If you get open, then there's no connectivity, which means you have a break somewhere. If it ohms out fine, then your ECU is the cause.