In place of earlier known sphericity testing techniques using accurate reference surfaces which are compared with a surface under test, this invention provides an absolute test of sphericity by making use, in effect, of the spherical wavefronts emanting from or converging to a point. A hologram plate is illuminated with coherent light from a laser to establish a first beam which forms a virtual image at the same point as that at which a beam illuminating the surface under test is focused, the illuminating beam being reflected at the surface and forming with the first beam observable interference fringes indicative of departures of the surface under test from true sphericity.