Method for testing a test piece for the presence of a leak using a foil chamber, wherein the foil chamber has walls having at least one flexible wall region to which a measurement volume adjoins and is arranged on that side of the flexible wall region opposite the foil chamber volume and is hermetically separated from the foil chamber volume, having the following steps: placing the test piece in the foil chamber, closing the foil chamber, evacuating the foil chamber and monitoring the measurement volume during evacuation of the foil chamber, using the result of the monitoring to reach a conclusion regarding the magnitude of a leak, characterized in that a venting valve connecting the measurement volume to the atmosphere is closed when the pressure in the measurement volume is below a predefined threshold value, and is opened as soon as the pressure exceeds the threshold value.