Are there also online tests?
Yeah, and not too close. Various agencies offer self-tests and questionnaires on the Internet. How serious and sound these tests are depends on the provider.
The questionnaires created by experts, such as those of the WHO (World Health Organisation), are much more reliable than the self-tests of parenting magazines and the like. However, as already mentioned, no such test can cover all patients or interpret the symptoms with certainty as ADHD. The online questionnaires therefore do not replace a visit to the doctor.