At a junior high school, what you learned was regularly verified in the form of examinations. The exams are also a way to verify whether you understand. If you already graduated from school, examination for qualification acquisition is a similar way for verification.
In areas where knowledge is not changing rapidly, and good textbooks exist, the verification by test works well. On the other hand, if the change is rapid, textbooks and exams become obsolete rapidly. Textbooks and exams do not cover the knowledge necessary for practical use.