Astronomical aspherical mirrors may be tested in the optical shop with a Hartmann null test. A null test is obtained by placing small wedges over each hole of the Hartmann screen. The wedges have an angle between the two faces such that the spherical aberration with the object and the image at the center of curvature is just compensated.
Daniel Malacara, "Hartmann Test of Aspherical Mirrors," Appl. Opt. 11, 99-101 (1972)