Olusola O Adesope and colleagues conducted a meta-analysis to summarise the learning benefits of taking a practice test versus other forms of non-testing learning conditions, such as re-studying, practice, filler activities, or no presentation of the material.

Analysis of 272 independent effect sizes from 188 separate experiments demonstrated that the use of practice tests is associated with a moderate, statistically significant weighted mean effect size compared to re-studying (+0.51) and a much larger weighted mean effect size (+0.93) when compared to filler or no activities.

In addition, the format, number and frequency of practice tests make a difference for the learning benefits on a final test. Practice tests with a multiple-choice option have a larger weighted mean effect size (+0.70) than short-answer tests (+0.48). A single practice test prior to the final test is more effective than when pupils take several practice tests. However, the timing should be carefully considered. A gap of less than a day between the practice and final tests showed a smaller weighted effect size than when there is a gap of one to six days (+0.56 and +0.82, respectively).

Source: Adesope, O. O., Trevisan, D. A., & Sundararajan, N. (2017). Rethinking the Use of Tests: A Meta-Analysis of Practice Testing. Review of Educational Research, 87(3), 659-701.