credit to Jacob follow him here on miiverse, when ur in the weapon testing room go up the stairs/ramp and look up and to the right of the wall, and there should be a basketball net make sure the weapon u r testing has a bomb as the sub weapon. Like the splatershot jr. Aim ur bomb into the net and then relese. if ur bomb falls through the net, a splat of green ink will acour as well as a sound.