"Slippery Slope" can be found within the pages of Star Wars Tales 15 and has been compiled into Star Wars Tales Volume 4.
During a training session between Luke Skywalker and Yoda on the planet Dagobah, a droid bounty hunter by the name of Milko shows up, seeking to claim the reward offered by the Galactic Empire for Luke's capture. Yoda instructs Luke to prevent Milko from succeeding, warning that failure would expose their whereabouts and spell disaster for the Rebellion. Luke succeeds in apprehending Milko, but chooses to release him rather than execute him, making it clear that revealing Yoda's location would also mean admitting he was humiliated by a Jedi instead of capturing his target. The story concludes with Luke contemplating whether this encounter was a test orchestrated by Yoda, and if he had succeeded or failed.