Over a century of research has established practice testing as a highly robust learning strategy that promotes long-term retention. However, learners do not always appreciate the benefits of testing for memory and do not use it as effectively as they could during their own self-regulated learning. The goal of this review is to identify common themes from research focused on learners' metacognition about practice testing using the three components of metacognition (i.e., beliefs, monitoring, and control) as an organizational guide. To foreshadow the key findings from this research: (1) without support, learners lack metacognitive awareness of testing as a tool to enhance memory but do recognize that testing can be used as a monitoring tool; (2) learners can accurately monitor their learning while using practice testing when judgments are made in contexts that are representative of those encountered during a criterion test; (3) in educational contexts, learners report using less effective strategies equally or more often than practice testing; and (4) learners tend to test themselves only under conditions that encourage retrieval success, and rarely use a strategy involving repeated successful retrieval even when it would lead to improved retention. After reviewing research findings, I discuss various interventions that lead to learners using testing more often and more effectively in their own learning and offer recommendations for future research.