Recently, the testing effect has received a great deal of attention from researchers and educators who are intrigued by its potential to enhance student learning in the classroom. However, effective incorporation of testing (as a learning tool) merits a close examination of the conditions under which testing can enhance student learning in an authentic classroom setting, where a number of factors may deviate from the laboratory. Based on existing evidence, we highlight several studies that encompass a few of the complexities of using testing to enhance course performance, including situations in which quizzing is beneficial for summative test performance, contexts in which quizzing does not appear to be as beneficial, and instances in which quizzing may actually hamper final test performance.