No, you can not trust the built-in speed test in the Ubiquiti Unifi Security Gateway or the controller. Here are some rather simple test that I made.
First of all, my internet connectivity is probably above average. I have two ISPs where the primary is a 1000/1000 connection (WAN1 on the USG) and the secondary is a 250/50 connection (WAN2 on the USG).
Everything in my network is connected by cable. Incoming internet is delivered to me with either standard gigabit ethernet cable (cat-6) or via a coax connected cable modem. All computers and devices at home are connected by cable too except mobile phones and tablets. These tests except the controller test is made using my iMac connected like:
iMac -> Unifi Flex Mini -> Unifi US-8 -> Unifi Security Gateway -> Internet
This is the built in speed test in my Unifi Controller (version 188.8.131.52) running on a Raspberry Pi 3B:
So yes, just under 200/200 isn’t that impressive on a supposed 1000/1000 connection. But I know I have downloaded files much, much faster than that. Something is not quite right here. Let try a test from my computer. As I’m Swedish there is a local initiative called Bredbandskollen (http://www.bredbandskollen.se/) which is the go-to test that most ISPs recommend here. Lets see what I get there:
Wow, 900Mbps and less than a millisecond in latency! That’s more like it. And this also proves that the USG very well can handle speeds up to gigabit without much problems (provided the correct settings, I have “Protection Mode” set to “Disabled” as afaik it doesn’t do much anyway other than provide a false sense of security).
But one test is no test (well, now we have two tests that shows different results) so I did a few more. Note that these tests were done while my home network was resonable un-quiet with many browser tabs open, Spotify playing music etc.
FAST (http://fast.com) is the one that is recommended by Netflix I think. Gives very similar results to Bredbandskollen.
Conclusion: Don’t ever trust the built-in speed test that the USG and/or controller provides (unless you have a sub-100 Mbps connection I guess). Always (and I can not stress this enough) do the tests with a wired connection. Going wireless introduces so many variables that is hard to control. Always do at least two (three) tests using different services. These tests are of course only showing the speed I get at one point in time and if I suspected variance I would have to do more tests of a longer time period.
Bonus information for me: I really get the promised 1000/1000 speeds that my primary ISP is selling me.