Testing network speed on macOS:

networkQuality

Example output:

Downlink: capacity 24.052 Mbps, responsiveness 321 RPM - Uplink: capacity 0.000
Downlink: capacity 24.052 Mbps, responsiveness 294 RPM - Uplink: capacity 20.669
Downlink: capacity 24.548 Mbps, responsiveness 250 RPM - Uplink: capacity 20.669
Downlink: capacity 24.548 Mbps, responsiveness 248 RPM - Uplink: capacity 17.763
Downlink: capacity 26.099 Mbps, responsiveness 243 RPM - Uplink: capacity 17.763
Downlink: capacity 26.099 Mbps, responsiveness 243 RPM - Uplink: capacity 16.716
Downlink: capacity 26.567 Mbps, responsiveness 240 RPM - Uplink: capacity 16.716
Downlink: capacity 26.567 Mbps, responsiveness 240 RPM - Uplink: capacity 16.632
Downlink: capacity 27.436 Mbps, responsiveness 237 RPM - Uplink: capacity 16.632
Downlink: capacity 27.436 Mbps, responsiveness 235 RPM - Uplink: capacity 15.908
Downlink: capacity 27.120 Mbps, responsiveness 194 RPM - Uplink: capacity 15.908
Downlink: capacity 27.120 Mbps, responsiveness 185 RPM - Uplink: capacity 16.711
Downlink: capacity 25.164 Mbps, responsiveness 156 RPM - Uplink: capacity 16.711
Downlink: capacity 25.164 Mbps, responsiveness 150 RPM - Uplink: capacity 16.939
Downlink: capacity 24.892 Mbps, responsiveness 124 RPM - Uplink: capacity 16.939
Downlink: capacity 24.892 Mbps, responsiveness 118 RPM - Uplink: capacity 17.627
Downlink: capacity 23.011 Mbps, responsiveness 108 RPM - Uplink: capacity 17.627
Downlink: capacity 23.011 Mbps, responsiveness 100 RPM - Uplink: capacity 15.339
Downlink: capacity 22.093 Mbps, responsiveness 87 RPM - Uplink: capacity 15.339
Downlink: capacity 22.093 Mbps, responsiveness 85 RPM - Uplink: capacity 13.592
Downlink: capacity 23.291 Mbps, responsiveness 63 RPM - Uplink: capacity 13.592
Downlink: capacity 23.291 Mbps, responsiveness 63 RPM - Uplink: capacity 14.177
Downlink: capacity 23.291 Mbps, responsiveness 43 RPM - Uplink: capacity 17.627 
==== SUMMARY ====
Uplink capacity: 17.627 Mbps
Downlink capacity: 23.291 Mbps
Responsiveness: Low (43 RPM)
Idle Latency: 19.708 milliseconds