Here is an excellent article from MuniNetworks that provides an excellent overview of the problems with broadband speed tests. It is easy for service providers to spoof speed tests into reporting higher upload and download speeds than anyone actually gets on a daily basis.
Speed tests are a bit of a problem for community-owned networks, as they generally don't show the dramatic performance improvements of the local network, because the speed test servers are located somewhere else on the Internet. So it is hard to show just how much better the local network is compared to an incumbent network. The solution is for the community network to install a speed test server on the local network, where the full bandwidth can be shown without the latency of the public Internet.