Teaching software testing and debugging is a critical yet challenging task in computer science education, often hindered by low student engagement and the perceived monotony of these activities. Sojourner under Sabotage, a browser-based serious game, reimagines this learning experience by blending education with an immersive and interactive storyline. Players take on the role of a spaceship crew member, using unit testing and debugging techniques to identify and repair sabotaged components across seven progressively challenging levels. A study with 79 students demonstrates that the game is a powerful tool for enhancing motivation, engagement, and skill development. These findings underscore the transformative potential of serious games in making essential software engineering practices accessible and enjoyable.