When you test your memory of a detail, that strengthens your memory of the detail.
Experiment has demonstrated this effect even when the correct answer is not provided, and even when the test-taker is given “open-book” access to find a correct answer. The effect has been demonstrated in many fields and at many age levels.
Branwen, G. (2009). Spaced Repetition for Efficient Learning. Retrieved December 16, 2019, from https://www.gwern.net/Spaced-repetition