this is suppose to be "top secret" flight center,but in heavely populated area?what if the aircraft suffer from mid flight mulfunction ,and crash into street or building below?
unless,it was intentional,for public relation .
China has very high standard of air safety for their new generation of fighter jet and it will not crashed.
If you can read Chinese. There is a banner on top of the test building that says it all... The wording is there not for show only. Its to drill into every personnel involved in J-20 project.
Plus its no more top secret eversince China acknowledge its existence.