They can't check unless they have real stealth planes
Of which they have none. Su-57 is about as stealthy as a clean Rafale with maybe a slightly better frontal RCS. It's not good enough to simulate RCS of B2, F-35, or F-22. Maybe also not J-20 if surface looks are anything to go by. But of course the fanboys will cry about it not being anything. The J-20 is a shit copy of Mig-1.44 made out of cardboard. The irony is this is actually good for China. The more these people, wherever they are, bury their heads in the sand while remaining anti-China in every matter, the further they fall behind in reality and the less they realise how much others have improved and how far they've fallen. The race is not over, in fact it has barely started and these morons are patting themselves on their backs.