This test is free, fast and there are 20 questions.
It will only take you about 20 minutes to finish it. However, your result will not only depend on your answers, but also on the time you take to complete the test.
If you don't find the answer, you can also pass the question and come back to it later (note that the questions list is always on top of the pages).
Getting a pen and a paper can be useful, but is not essential ! On the other hand, no computer must be used, in which case you would distort your result.