Research over the past few decades points to ways precalculus and calculus courses can be strengthened to improve student learning in these courses. This research has informed the development of the Algebra and Precalculus Concept Readiness (APCR) and the Calculus Concept Readiness (CCR) assessments. In this article, the authors present three sample tasks from these instruments--the Oil Spill problem, the Free Throw problem, and the Ladder problem--that require an understanding of functions to represent the relationship between quantities. Commentary on student responses serves to identify foundational reasoning abilities and may help teachers develop curriculum to support student achievement.