Quality assessment of student learning is important in physics education. However, it can be challenging to construct assessments measuring students' understanding of concepts and elicit deeper levels of cognition during problem solving. Tests are common assessments, but students assume test questions will have a numeric or symbolic answer. This study analyzes test responses and reflections on a question without a numeric or symbolic answer from a calculus-based physics class. Though designed to test conceptual understanding, students' assumptions and expectations about test questions hindered their ability to accurately represent their understanding.We analyzed students' responses and short reflections on the problem by looking at ways students tried to solve the problem and their uncertainties when confronted by a non-traditional test question. Using a framework of epistemic resources, we found that students used a variety of resources to pursue a solution; though common patterns emerge that can inform instructors and physics education researchers.