Sleep right after studying new material is more conducive to memory than a period of wakefulness. Another way to counteract forgetting is to practice retrieval: taking a test strengthens memory more effectively than restudying the material. The current work aims at investigating the interaction between sleep and testing by asking if testing adds to, neutralizes, or decreases the effect of sleep on memory? We tested this in one pilot and one experiment by manipulating the timing of the practice test as well as whether practice was followed by sleep or wakefulness when learning foreign language vocabulary. Taking a delayed practice test significantly reduces forgetting for both the sleep and the wakefulness group. An immediate practice test, in contrast, had no such effect; here we find the standard beneficial sleep effect. However, the immediate practice test leads to higher recall in the final test in comparison to a delayed practice test, but only for the sleep group. Practical recommendations imply two things: first, if students study in the evening, they should test themselves immediately after learning. Second, if students study during the day the practice test should be delayed in order to reinforce memory and reduce forgetting of the material.