Abstract: In a testing system for chemical substances or substance mixtures, especially for potential plant protection compositions, the chemical substance to be tested or the substance mixture to be tested is applied to a test specimen, especially to plants or parts of plants. When a predetermined period of time has elapsed, the test specimen is examined for the activity of the substance or substance mixture. For this purpose, first of all a type of test specimen is selected from a stock of test specimens, and the substances to be tested are selected from a stock of substances to be tested. The selected type of test specimen and the selected substances are identified (BC1, BC2) by means of a machine-readable code and those codes are supplied to a memory unit (12).