ISPs happily collaborate with and put speed test servers in privileged locations on their network so you will get higher speeds there even if the actual peering to the outside world is much slower.
You can try Fast.com (Netflix) or Cloudflare’s one which are explicitly designed to work around this by serving the test data from the same endpoints the serve actual customer data, so ISPs can’t cheat.
This still doesn’t guarantee however that you will achieve this speed to any random host on the internet - their pipe to Cloudflare/Netflix may very well be fat and optimized but it doesn’t guarantee their pipe to a random small hosting provider doesn’t go over a 56k modem somewhere (I jest.. but only a bit).
Given that whether you get 30mbit or 30gbit from Netflix won’t make a blind bit of difference it’s not that useful a test. It doesn’t do upload either as Netflix is all about consumption.
Test to where you want to exchange high speed traffic.
