It’s a tough one. I don’t know what their policies are regarding the 'pass' mark for aptitude. I wouldn’t imagine it’s very high - they are a business at the end of the day. But, they can’t just let anyone in either, they surely need to do some degree of vetting, otherwise their failure rate wouldn't look too promising.
I'd go modular too - but that’s a different debate entirely! I guess doing one of these aptitude tests is really the only way of having a taste of a selection process - you said you have never had an interview, so it’s probably a good place to start, and you will get some feedback regarding your performance.
I can’t really see any other way of ‘checking’ you aptitude and ability to become a professional pilot.
Don’t forget, all these schools want to sell you their product, so the chances are there won’t be many people that tell you you’re not up to it.