According to the "Standards for Educational and Psychological Testing" (2014), one aspect of test fairness concerns examinees having comparable opportunities to learn prior to taking tests. Meanwhile, many researchers are developing platforms enhanced by artificial intelligence (AI) that can personalize curriculum to individual student needs. This leads to a larger overarching question: When personalized learning leads to students having differential exposure to curriculum throughout the K-12 school year, how might this affect test fairness with respect to summative, end-of-year high-stakes tests? As a first step, we traced the differences in content exposure associated with personalized learning and more traditional learning paths. To better understand the implications of differences in content coverage, we conducted a simulation study to evaluate the degree to which curriculum exposure varied across students in a particular AI-enhanced learning platform for Algebra instruction with high-school students. Results indicate that AI-enhanced personalized learning may pose threats to test fairness as opportunity-to-learn on K-12 summative high-stakes tests. We discuss the implications given different perspectives of the role of testing in education