A testing device, comprising: one or more radio frequency RF frontends, wherein each RF frontend, of the one or more RF frontends, includes a respective transmitting port and a respective receiving port; one or more power splitters, wherein each power splitter, of the one or more power splitters, is connected to a respective RF frontend of the one or more RF frontends; and one or more processors configured to: receive, via a receiving port of a particular RF frontend, of the one or more RF frontends, a downlink pilot signal on a downlink channel; determine a phase associated with the downlink pilot signal; transmit, via a transmitting port of the particular RF frontend and based on one or more transmission settings, an uplink pilot signal on an uplink channel; receive, after transmitting the uplink pilot signal on the uplink channel, the uplink pilot signal via the receiving port of the particular RF frontend and a particular power splitter, of the one or more power splitters, associated with the particular RF frontend, wherein the one or more processors, when receiving the uplink pilot signal, are configured to receive the uplink pilot signal via an external circuit connected to the particular RF frontend and a particular RF frontend of a base station; determine, after receiving the uplink pilot signal, a phase associated with the uplink pilot signal; determine a phase difference between the phase associated with the downlink pilot signal and the phase associated with the uplink pilot signal; determine that the phase difference between the phase associated with the downlink pilot signal and the phase associated with the uplink pilot signal satisfies a threshold; and adjust, based on the phase difference between the phase associated with the downlink pilot signal and the phase associated with the uplink pilot signal satisfying the threshold, the one or more transmission settings. one or more radio frequency RF frontends, wherein each RF frontend, of the one or more RF frontends, includes a respective transmitting port and a respective receiving port; one or more power splitters, wherein each power splitter, of the one or more power splitters, is connected to a respective RF frontend of the one or more RF frontends; and one or more processors configured to: receive, via a receiving port of a particular RF frontend, of the one or more RF frontends, a downlink pilot signal on a downlink channel; determine a phase associated with the downlink pilot signal; transmit, via a transmitting port of the particular RF frontend and based on one or more transmission settings, an uplink pilot signal on an uplink channel; receive, after transmitting the uplink pilot signal on the uplink channel, the uplink pilot signal via the receiving port of the particular RF frontend and a particular power splitter, of the one or more power splitters, associated with the particular RF frontend, wherein the one or more processors, when receiving the uplink pilot signal, are configured to receive the uplink pilot signal via an external circuit connected to the particular RF frontend and a particular RF frontend of a base station; determine, after receiving the uplink pilot signal, a phase associated with the uplink pilot signal; determine a phase difference between the phase associated with the downlink pilot signal and the phase associated with the uplink pilot signal; determine that the phase difference between the phase associated with the downlink pilot signal and the phase associated with the uplink pilot signal satisfies a threshold; and adjust, based on the phase difference between the phase associated with the downlink pilot signal and the phase associated with the uplink pilot signal satisfying the threshold, the one or more transmission settings. receive, via a receiving port of a particular RF frontend, of the one or more RF frontends, a downlink pilot signal on a downlink channel; determine a phase associated with the downlink pilot signal; transmit, via a transmitting port of the particular RF frontend and based on one or more transmission settings, an uplink pilot signal on an uplink channel; receive, after transmitting the uplink pilot signal on the uplink channel, the uplink pilot signal via the receiving port of the particular RF frontend and a particular power splitter, of the one or more power splitters, associated with the particular RF frontend, wherein the one or more processors, when receiving the uplink pilot signal, are configured to receive the uplink pilot signal via an external circuit connected to the particular RF frontend and a particular RF frontend of a base station; determine, after receiving the uplink pilot signal, a phase associated with the uplink pilot signal; determine a phase difference between the phase associated with the downlink pilot signal and the phase associated with the uplink pilot signal; determine that the phase difference between the phase associated with the downlink pilot signal and the phase associated with the uplink pilot signal satisfies a threshold; and adjust, based on the phase difference between the phase associated with the downlink pilot signal and the phase associated with the uplink pilot signal satisfying the threshold, the one or more transmission settings.