A concern in engineering education is students adopting a 'recognise and reproduce' approach to problem solving. In this study, an assignment was conceived and analysed through Legitimation Code Theory -- which allows for visualisation of students' thinking, and to illuminate how students construct knowledge in open-ended problem solving. The assignment was based on students posing their own exam-style questions. Evidence for its subjective effect on the students was generated through students' responses to a questionnaire. Most (72%) students found the assignment assisted their understanding and context of the work, while 75% believed the open-ended nature of the assignment would make them better engineers. About 52% said they would change the way they study based on the insights and self-reflection from the assignment. While several students discuss an approach focussed on repetition, recognition, and algorithmic learning, the assignment showed students using an open-ended approach.