A test and/or calibration assembly for flowmeters, in particular for ultrasonic flowmeters, wherein the test and/or calibration assembly comprises: a U-pipe arrangement having two at least proportionally vertical pipe sections (3, 5) and one at least proportionally horizontal pipe section which connects the two at least proportionally vertical pipe sections (3, 5) to one another, in particular in their lower region; a fluid which fills the at least proportionally horizontal pipe section and projects into the two at least proportionally vertical pipe sections (3, 5) to form fluid columns there; a drive unit which is configured to move the fluid along the U-pipe arrangement so that a volume flow of fluid through the at least proportionally horizontal pipe section and, at the same time, a variation in the height of the two fluid columns in the two at least proportionally vertical pipe sections (3, 5) take place; and a control and evaluation unit which is configured to control the drive unit and to monitor the behavior of the fluid in order to determine an actually generated flow through the at least proportionally horizontal pipe section therefrom; wherein the at least proportionally horizontal pipe section has a test and/or calibration region in which the flowmeter to be tested and/or calibrated can be provided to measure a flow through the at least proportionally horizontal pipe section, wherein the control and evaluation unit can be coupled to the respective flowmeter to be tested and/or calibrated and is configured to compare the flow measured by the flowmeter with the actually generated flow and to output a corresponding result and/or to calibrate, in particular automatically, the flowmeter based on the actually generated flow, characterized in that the drive unit and the control and evaluation unit are configured to effect an oscillating variation, in particular a harmonically oscillating variation, in the height of the fluid columns in the two at least proportionally vertical pipe sections (3, 5) and thus a correspondingly oscillating flow through the at least proportionally horizontal pipe section. a U-pipe arrangement having two at least proportionally vertical pipe sections (3, 5) and one at least proportionally horizontal pipe section which connects the two at least proportionally vertical pipe sections (3, 5) to one another, in particular in their lower region; a fluid which fills the at least proportionally horizontal pipe section and projects into the two at least proportionally vertical pipe sections (3, 5) to form fluid columns there; a drive unit which is configured to move the fluid along the U-pipe arrangement so that a volume flow of fluid through the at least proportionally horizontal pipe section and, at the same time, a variation in the height of the two fluid columns in the two at least proportionally vertical pipe sections (3, 5) take place; and a control and evaluation unit which is configured to control the drive unit and to monitor the behavior of the fluid in order to determine an actually generated flow through the at least proportionally horizontal pipe section therefrom; wherein the at least proportionally horizontal pipe section has a test and/or calibration region in which the flowmeter to be tested and/or calibrated can be provided to measure a flow through the at least proportionally horizontal pipe section, wherein the control and evaluation unit can be coupled to the respective flowmeter to be tested and/or calibrated and is configured to compare the flow measured by the flowmeter with the actually generated flow and to output a corresponding result and/or to calibrate, in particular automatically, the flowmeter based on the actually generated flow, characterized in that the drive unit and the control and evaluation unit are configured to effect an oscillating variation, in particular a harmonically oscillating variation, in the height of the fluid columns in the two at least proportionally vertical pipe sections (3, 5) and thus a correspondingly oscillating flow through the at least proportionally horizontal pipe section.