Puts a real bot in a real Daily room, exactly as a Quarterzip call does. It greets you on arrival, then echoes your audio back a second and a half later. The main diagnostic can only measure media leaving this machine; this measures the whole round trip, plus whether your screen share actually arrives.
Wear headphones. On speakers you are testing your laptop's echo cancellation, not the network.
Not sharing. Start a share to test whether high-bitrate video survives this network — it is the first thing to fail when audio still works.