Angle dispersive X-ray diffraction is used to test pharmaceutical products including a dosage form inside packaging, for example a tablet inside a blister pack, without removing the dosage form from the packaging. The dosage form is aligned with a measurement system having an X-ray source for generating X-rays, X-ray optics, and an X-ray detector for detection of X-rays. Then, at least one X-ray signature is measured on a predetermined location on the dosage form. The measured X-ray signature is compared with reference X-ray signatures in a data library.