The invention relates to a method of filling nozzles (11) of a dispensing system (2) of a test system (1) comprising a dispensing system (2) and a microfluidic device (3) comprising at least the following steps: (a) transporting the solution from the container (6) via the nozzle (11) of the dispensing system (2) to the sample application opening (13) of the microfluidic device (3) by means of a micro-pump (10), (b) further transporting the solution into the measuring region of the microfluidic passage (14) of the microfluidic device (3), (c) measuring a light signal in the measuring region of the microfluidic device (3) by means of at least one photosensitive sensor (4) with a plurality of photodetectors (5), and (d) deactivating the micro-pump (10) when the light signal and/or a change in the light signal is detected.