This morning got a need to test an app in bad network conditions and this tool (found via @iosdevweekly) worked great:

https://macos-network-throttler.com/

Network Throttler — Throttle Network Speed on macOS for Testing

Throttle your Mac's network speed to test apps on slow, lossy, or unreliable connections. Simulate 3G, Edge, flaky WiFi, and more from your menu bar.

@aleck better than what is builtin in Simulator itself, or Proxyman? I always had trouble tuning those to something realistically bad…
@ristkof Can't compare to those as I did not use them. This has preset called "Very bad network" and it actually is horrible :) as my packets were barely transmitting. Main thing is that it's instant on/off so it's trivial to test. It has 7 day trial so you test it easily.