A test system for a plurality of transmissions is disclosed. Each of the plurality of transmissions may have a transmission input member and a transmission output member. The test system may have a prime mover. The prime mover may have a prime mover output member configured to connect to the transmission input member of each of the plurality of transmissions. Additionally, the test system may have a plurality of inertia devices. Each of the inertia devices may be configured to connect to the transmission output member of one of the plurality of transmissions via a drive shaft. The test system may also have a controller. The controller may be configured to communicate with the prime mover and the plurality of transmissions to control a transfer of power between the plurality of transmissions.