A base station testing apparatus, comprising: a beamforming network, comprising: multiple input ports configured to receive one or more input signals originating from one or more transceivers of a base station; and multiple output ports configured to receive signals from the input ports that is based on the one or more input signals, and to output, based on the signals, multiple output signals associated with a simulated beam direction, the simulated beam direction being a beam direction that would be produced by an antenna array of the base station in an operating scenario when fed with the one or more input signals; characterised by a feedback component configured to provide a feedback signal, that is based on one or more of the multiple output signals, to a calibration component of the base station; and a test component, wherein the multiple output ports of the beamforming network are configured to provide one or more of the multiple output signals to the test component, wherein the multiple input ports of the beamforming network are further configured to receive one or more phase-adjusted input signals based on the feedback signal. comprising: a beamforming network, comprising: multiple input ports configured to receive one or more input signals originating from one or more transceivers of a base station; and multiple output ports configured to receive signals from the input ports that is based on the one or more input signals, and to output, based on the signals, multiple output signals associated with a simulated beam direction, the simulated beam direction being a beam direction that would be produced by an antenna array of the base station in an operating scenario when fed with the one or more input signals; characterised by a feedback component configured to provide a feedback signal, that is based on one or more of the multiple output signals, to a calibration component of the base station; and a test component, wherein the multiple output ports of the beamforming network are configured to provide one or more of the multiple output signals to the test component, wherein the multiple input ports of the beamforming network are further configured to receive one or more phase-adjusted input signals based on the feedback signal. multiple input ports configured to receive one or more input signals originating from one or more transceivers of a base station; and multiple output ports configured to receive signals from the input ports that is based on the one or more input signals, and to output, based on the signals, multiple output signals associated with a simulated beam direction, the simulated beam direction being a beam direction that would be produced by an antenna array of the base station in an operating scenario when fed with the one or more input signals; characterised by a feedback component configured to provide a feedback signal, that is based on one or more of the multiple output signals, to a calibration component of the base station; and a test component, wherein the multiple output ports of the beamforming network are configured to provide one or more of the multiple output signals to the test component, wherein the multiple input ports of the beamforming network are further configured to receive one or more phase-adjusted input signals based on the feedback signal.