Serious games have the potential to complement existing teaching methods by motivating and providing a more enjoyable experience for the players or by simulating events that would be otherwise difficult to reproduce in the classroom. Despite their potential, little is known about how the games could be used not only for teaching but also as assessment tools. This research addresses this gap. We present an in-game assessment method which assesses the learning objectives included in the game without the need for a separate intervention. We evaluate the proposed method and we show that there is no statistically significant difference in participants being assessed through a questionnaire outside the game and the integrated game assessment method. Moreover, we looked at whether the player experience has been affected by the changes needed in the game design and the players' preferences for different types of assessment. Most participants preferred being assessed through the game. They also felt that the assessment has overall improved their game experience.