Then they should be flying near Southern Borders. You will have gazillion breaking news snippets on the internet in 10 minutes xD, detected by next gen state of the art Martian AESA wide array 56" Modi radar.Some neighbors will make noise on media that they detected chinese presence near their territories. Some even like to brag that they detected J-20. Remember India?
I personally think Chinese would very much be testing the radar strengths in the neighbourhood, probably with a lot more and secretive tool kit than just J-20s alone.