|The following is based on developer test content cut from Fallout 3 and has not been confirmed by canon sources.|
DLC05TestUtility is a test cell in 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).
DLC05TestUtility appears in the game files of Mothership Zeta (add-on) but should not be considered canon because it is a test cell.