Math textbooks - you read the chapter, learn how to solve the problems, then attempt them and see if your answer matches the ones in the back of the book. Having a professor give you tests and grade them is optional but often useful.
If you already know parts of the material, you may want to take the tests provided in the textbook first, and then focus on the material associated with the problems you did not solve correctly.
A lot of my significant personal improvement happened as a result of highly measurable progress and tight feedback loops. For example: