Brake pedal goes to floor with engine running

I had the caps on the mc. I made the mistake of pumping the brake pedal once and shot a bunch of fluid out. I didn't try pulling the hose off the booster to see if it hisses. I checked the booster according to the manual and it checked out good without any leaks but I will try pulling the hose off and see what happens. The calipers are installed correctly. That is one of the first things I checked. I made sure the mc did not get too low when bleeding so it didn't get air and I had to start over. With the engine off and after a couple pumps the booster is empty and the pedal barely goes down and feels firm. As soon as I start it the pedal will go to the floor and there isn't much there. I have another booster but it is used. Is there any way to bench test it before changing it? They are not that fun to change because it you need 4 elbows and 2 thumbs on one hand to get at the bolts. My new mc will be here tomorrow so It would be a good time to change the booster too if I knew the other one is good. Thanks for the support so far. I appreciate it.