I would try a small live hopper mouse. Put it in the enclosure with complete darkness in the room and in the enclosure. Then when you can't see a thing get to the side wheres your snake can't see you and just listen and wait. If you hear the mouse squeal then you will know it worked. Wait a bit for it, if there is no squeal then turn on the lights and check on things. I would give it a fair chance though first. Some snakes would rather eat in complete darkness, you can't see a thing darkness. Letting the smell of the feeder be in the room beforehand is a great help.