It's too complicated. It has something to do with the mind and body, and it's relationship, regardless it's outcome from of those factors.
Only something biological and live, like, brain scanning, or certain tests that are accompanied by something similar would certainly do the job -- not 'just' some tests, online or otherwise.
All I know is that it has little to do with results of circumstances, preferences, upbringing, inclinations, functioning level, milestones reached or achieved, behaviors, levels of competence or aptitude, actions done, personalities, outlook, lifestyles, maturity, and so on -- those that are only accountable by the odds of likely/unlikely of being autistic/allistic.