The authors present the results of quantitative data and student feedback from a two-year study of the effects of a new assessment model called "mastery-based testing." In mastery-based testing, students are given problems in which they can only receive full credit for the problem after they demonstrate mastery of the objective being assessed. This method strives to increase complete understanding of concepts through a growth-mindset approach to learning in addition to helping alleviate math anxiety. In this study, we compare the impact of mastery-based testing with traditional testing in six Calculus II classes. The data sources for the project included end-of-semester surveys, a final mastery assessment, and end-of-semester course grades. We found that mastery-based testing led to students feeling the assessments better reflected their content knowledge as well as higher end-of-semester course grades with fewer hours spent studying outside of class.