A method for testing a monitoring device (20) of an automatic labeling machine (10) for containers (12) for correct functioning, in the case of which, a specially marked measuring container (14) is fed thereto, upon whose detection, a labeling process is discontinued at least for this measuring container (14), and the measuring container (14) provided with markings (16) is scanned by at least one optical sensing device (21) of the monitoring device (20).