Prior to the Galactic Civil War, the Galactic Empire engineered a test unit version of the Death Star. This model was built with the purpose of validating the battlestation's design.
The Rebel Alliance, during the Galactic Civil War, mistakenly targeted the test unit, thinking it was the real Death Star. They breached the defenses, overcoming the Stormtroopers guarding it, and made their way to the control room. There, they learned the station's true nature. Following the Rebel success, Imperial forces abandoned the station. Subsequently, Darth Vader commanded the station's self-destruction.
This version of the Death Star made its debut in the mobile card game Star Wars: Force Collection, available on Android and iPhone. The test unit served as the setting for the "Battle of the Death Star Campaign," which concluded on September 25, 2013. The Light Side emerged victorious at the campaign's end.