Yes they have, both the PLAAF Dingxin Flight Test & Training Base and Cangzhou Flight Training Base, but at least by all know, each regular type was first tested at the factory, then at the CFTE at X#An-Yanliang and the both PLAAF Flight Test & Training Bases.
Thsi IMO however would never be unnoticed, since for XAC, where the H-20 is designed and built, this is both at Xi'an-Yanliang and I cannot think of a stealth bomber being secretly rolled out, secretly test flown only at night thru all the years at Yanliang without any rumour.
Now one could argue, the H-20 is not a regular type and maybe there is a secret XAC factory somewhere hidden under mountains far far away near a similar secret flight test facility, ... yes, there could also be already a secret moon base where the PLA Space Force tests cloaking devices and photon-torpedoes.