How useful/effective are online self-assessment tests

  Because we live in 21 century, internet is our part of life. So with the help of it , we can assess ourselves in many ways. For example, psychological,  educational, medical , mathematical and etc. However, we often use educational self-assessment during our learning period. It is very useful and you will do it privately , no one can see your results except you. And besides you can know your level in learning languages , for example. There are many online test for us to do in every level, A1 A2 B1 B2 C1 C2. For applicants, there are block test on the internet in order to try themselves before the exam. I think these things will work for our prosperious future .