This is fairly new but it has been done over the years to check stability of the wifi drivers in particular. Its usefully to perform load tests after major openwrt version updates and/or opkg changes.
Start the server on the openwrt AP:
iperf3 -s
Note: If you want to run multiple clients you need to have them on separate ports
Run the net_laodtest.sh script, defaults should be fine but you can overwrite the IP
and the port number if need be:
bash openwrt/scripts/local/net_loadtest.sh
NOTE: it will run continously and log to results-.log