I always wondered why China doesn't flood foreign war zones with weapons to field test their fancy new gear against the USAF. Seems like a no-brainer.
They sell them. Military gear (at least aircraft and missiles) aren't cheap like an AK47. They have enjoyed watching India and Pakistan in their latest air battles. Lots of operational intel gleaned from that.
They do. India-Pakistan was basically a field trial of Chinese AD. It failed miserably but the Chinese blame operator error (which is still valuable info; there is no reason to assume a PLA ground operator would be more competent than a Pakistani one).