A method and an automated system for testing liquid samples comprising a reaction vessel transferring device are presented. A first analytical unit for running a first diagnostic test comprises a rotatable first vessel holder detachably holding reaction vessels. A second analytical unit for running a second diagnostic test comprises a stationary linear second vessel holder detachably holding reaction vessels. The transferring device comprises a gripper for gripping a reaction vessel and transfers reaction vessels from the first vessel holder to the second vessel holder and/or vice versa. The device is translatable parallel to the second vessel holder and the gripper moves along a curved path between a picking position and a reaction vessel seat of the second vessel holder.