|The following is based on developer test content cut from Fallout 3 and has not been confirmed by canon sources.|
DLC05TestMachineCombos is a test cell for mothership Zeta that can only be accessed by using console commands.
The console commands to enter these rooms are COC <cell name>, as it can only be accessed by console commands it must also be exited this way (i.e. COC DLC05EngineCore).
DLC05TestMachineCombos features various alien machine and structural prefabs.
DLC05TestMachineCombos appears in the game files of the Fallout 3 add-on Mothership Zeta but should not be considered canon because it is a test cell.