Abstract: The invention relates to moment bearing test device and a method of testing a wind turbine moment bearing. The test device comprises a drive unit for rotating a first ring relative to a second ring of the moment bearing. The drive unit is mounted to at least one torque arm rotatably connected to a mounting frame. The mounting frame is configured to be mounted to the first or second ring. The test device further comprises a measuring unit for measuring a friction torque of the moment bearing. The test device acts as a mobile test device allowing the test to be performed on-site and allows the moment bearing to be tested when mounted to the rotor hub or mainframe.