A testing device for detecting defects of transparent test specimens, in particular of ophthalmological lenses, has an illumination device for transilluminating test specimens to be examined and with an image acquisition device for imaging the test specimen transilluminated by the illumination device. The illumination device includes a plurality of linearly adjustable light sources for generating a stripe pattern. To capture the stripe pattern, the acquisition duration of the image acquisition device can be adjusted in such a way that the light emitted by each of the light sources is detected as a light stripe. Further, the disclosure relates to a testing method for detecting a defect of a transparent specimen.