An apparatus (10) comprising means for: enabling testing of at least one user equipment (110, 12) over a plurality of radio frames by: determining (202), for at least one candidate position in a current radio frame, if one or more signals are to be transmitted to the at least one user equipment, based, at least in part, on one or more probabilities associated with the at least one candidate position in the current radio frame; if it is determined, for at least one candidate position in the current radio frame, that one or more signals are to be transmitted to the at least one user equipment, transmitting (204) one or more signals to the at least one user equipment using the at least one candidate position in the current radio frame; if it is determined, for at least one candidate position in the current radio frame, that one or more signals are not be transmitted to the at least one user equipment, determining (206) if a maximum number of transmission failures has occurred, wherein a transmission failure is determined to have occurred when it is determined that no signals are to be transmitted in a current radio frame; and if it is determined that a maximum number of transmission failures has occurred, transmitting (208) one or more signals to the at least one user equipment using at least one candidate position in the current radio frame.