Abstract: A test procedure or test station for testing products, especially products completed on an assembly line type production process, performing the following steps: First, testing a parameter of a product with a first testing device using a first input signal to produce a first test result. Second, testing the same parameter of the product with a second testing device using a second input signal that is independent of the first input signal to produce a second test result. Third, deriving a differential value from the test results obtained by the testing devices. Fourth, determining the conformance of the testing station from the differential value and outputting an error message when the differential value deviates from a predetermined range. Fifth, repeating above steps for at least one other parameter.