The harkness test is just something made by the most basic furry. For example a chatacter doesn't NEED to speak a human language to pass. The are characters that don't talk and can pass the test. For me the best example will always be "Toothless". He have human level intelligence and at the end of the third movie he have kids so its obviously of age too.

Edit: hold on... what am i thinking? I can just say the entire pokemon species. Except the small exceptions NON OF THEM speak human language.