A testing device for testing an inner surface of a rotationally symmetrical cavity in a workpiece has a measuring head which defines an axial direction, and on which an optical system is situated. The optical system is in image transmission connection with an image recorder and a downstream evaluation apparatus. The testing device also has an illumination arrangement for illuminating an imaging area of the inner surface which is detected by the optical system. The illumination arrangement is designed and configured for illuminating the inner surface which is detected by the optical system. The illumination arrangement can illuminate the inner surface to be tested from different illumination directions in order to generate shadow images of the topography of the inner surface. The evaluation apparatus is designed and configured for determining the topography based on the shadow images recorded by the image recorder.
