Method and arrangement for determining a mass flow of an injection process of an injection valve

An arrangement comprises a test volume (22) and a cut-off valve (24). The test volume (22) is hydraulically arranged between the injection valve (20) and the cut-off valve (24). The cut-off valve (24) is hydraulically coupled to a fluid line (26). The method comprises the following steps: - opening the cut-off valve (24) while the injection valve (20) is closed, - closing the cut-off valve (24), - determining a first value (P_1) of the pressure in the test volume (22), - opening the injection valve (20) while the cut-off valve (24) is closed, - closing the injection valve (20), - determining a second value (P_2) of the pressure in the test volume (22), - determining the value (”P) of the pressure difference between the first value (P_1) and the second value (P_2), and - determining the mass flow (MFF) of the injection process of the injection valve (20) depending on the value (”P) of the pressure difference in the test volume (22).