This paper proposes a technique to encourage the interest of students in learning formal methods. Our course is focused on the B method, involving basic knowledge of set theory, invariance proofs, refinement techniques and so on. While lectures and tutorials cover a large range of such concepts, the practical work is focused on applying the principles of a model-based approach in the context of test generation. This paper explains the pratical outcome of the course, through the Leirios Test Generator tool, that gives an interesting and playful use of the B method, by simulating the execution of the model through animation, and by generating tests –based on the B model– that can be run on an implementation. In order to make sure that students will be interested in applying these techniques, we challenge them to play a game consisting in detecting mutants of a program with their model-based tests. The feedback from the students is very positive here, and suggests that formal methods are more likely to be understood if their interest is shown through a concrete application.