Test Cart The Test Cart is a test and diagnostic cartridge for the Vectrex. Various functions are supported based mainly around testing display alignment and intensity, controller functionality, and sound generation. A function to check the installed BIOS checksum is also included. The Test Cart is meant to be used along with the Vectrex Service Manual when repairing and testing the Vectrex game system. Also found later in 2000 was a single Overlay for use with the Test Cart. The Test Cart Overlay was acquired in a private sale from a former GCE employee. The Test Cart Overlay was scanned by Chris Romero and made available in 2001 for public usage, and later on Spike's Big Page.