ok sorry, too late to edit but i found that thing on wikipedia, so dont yell at the new guy im not sure if wikipedia is reliable
The ultimate test came one day when Maul was abandoned by his master on an isolated Outer Rim world, forced to survive alone while being hunted by hordes of assassin droids. After a month's time, Sidious returned and challenged his apprentice to a duel, one which Maul lost. Sidious then told Maul that he had been secretly training another apprentice to replace him. Rage and hatred overwhelmed Maul, and in one final act of defiance he nearly killed his master. When Maul's emotions were finally spent, he prepared himself for death, yet Sidious laughed instead. By wanting to kill his own master, Maul had in fact passed the final test. Sidious proclaimed him Darth Maul, Dark Lord of the Sith, and took him to a new home on Coruscant.