Apparatus, including a mockup cavity, simulating an actual body cavity of a human subject, wherein walls defining the mockup cavity comprise a tissue equivalent material (TEM). An array of electrodes are embedded in the walls. The apparatus further includes a programmable signal generator, connected to the electrodes, and configured to apply varying potentials to the array of electrodes so as to simulate electrophysiological potentials occurring in the actual body cavity on surfaces of the walls.