If you go into the tools page of a switch you'll see a throughput test - but you can't rely on this to max out the circuit. Also it just does a one of test. You should use a third party tool to verify throughput.
Strangely enough, as per Meraki support, the throughput test is not a test to test your internet speed.
That being said, I've noticed the throughput tests on the MR and MX series to provide a more accurate estimation of the internet speed than the switches for some reason. So if you can test using a downstream MR or an upstream MX you'll likely get a better result (even if that AP has to go through the switch).