I was just troubleshooting some injectors last night and what I did was buy a cheapo 6 pack of those little clear plastic water bottles. I emptied em, pulled the fuel rail, surrounded each injector with a bottle. I had to twist some of the injectors to get the plugs to reach the harness with the rail pulled out. I unplugged the coil pack and then had somebody turn the engine over and watched for the pattern. Worked great. You could tell both from seeing the spray and also from the quantity of fuel in each bottle. Wear safety glasses, no spark/fire nearby, and keep an extinguisher handy. If you have a leaky injector you may not even need to turn over the motor, just pressurize the rail by putting the key in the run position a few times and see if any are dripping.
'98 TJ (see profile)
'88 YJ with 4.0/AW4 swap & CJ front end
'80s CJ Resto-mod ('80s CJ frame/front end, YJ tub, '00 XJ 4.0)
'99 XJ 4dr SE