If assessment is the purpose of testing, open-book tests may defeat the purpose. However, a goal of education is to build knowledge, and based on the literature, open-book tests may not be inferior to closed-book tests in promoting long-term retention of information. Participants studied Swahili-English pairs and either re-studied or took an initial quiz, which was cued recall or recognition in an open-book or closed-book format. One week later, the final closed-book recognition test showed higher performance in the quizzed conditions than in the study-twice condition, replicating the testing effect. However, performance was similar across the quizzed conditions, indicating that testing promoted long-term retention regardless of test format (open-book versus closed-book) and test type (cued recall versus recognition). Open-book tests are not inferior to closed-book tests in building knowledge and can be particularly useful in online classes because preventing cheating is difficult when closed-book tests are administered online.