iPerf3

iPerf3 (and iperf2) is installed and running automatically on boot

Find a partner, run an iPerf test between 2 WLAN Pi's

1 - Perform a send throughput test

iperf3 -c  <x.x.x.x>

2 - Peform a reverse test

iperf3 -c  <x.x.x.x> -R

More details

iPerf - iPerf3 and iPerf2 user documentationiperf.fr