We demonstrate a method for testing optics (spherical and aspheric) and other reflecting or transmitting objects. We call this experimental ray tracing. A laser beam is sent through the sample, and its propagation is determined with a lateral effect photodiode. A modified Hartmann test can be performed by measurement of beam location within two planes. Measurement in one plane close to the focus delivers a spot diagram. The method is well suited for testing even strong aspheric optics. As a further use we demonstrate 3-D shape measurement of nonplanar glass plates, e.g., car windshields.