  We used an atom interferometer for atom optical shop testing of lenses for
atomic de Broglie waves. We measured focal lengths and spherical aberrations of
electrostatic lenses in three independent ways based on contrast data, phase
data, or calculations of de Broglie wavefront curvature. We report focal
lengths of -2.5 km and -21.7 km with 5% uncertainty for different lenses. All
three methods give consistent results. Understanding how lenses magnify and
distort atom interference fringes helps improve atom beam velocity measurements
made with phase choppers [New J. Phys. 13, 115007 (2011)], which in turn will
improve the accuracy of atomic polarizability measurements.
