Supposedly Fengbubei said there will be more news tonight (China time). I'm still thinking it's the J-10B handover ceremony, but CJDBY has it on authority that the fighter in question was yellow skinned and has a 3 digit number so ... that rules out the J-10B ...
Or perhaps it's a prototype J-10B flying with the WS-15 .. that would be even more exciting ..
They wouldn't use the J-10 to test engines. There was a pic of primer coloured J-10B prototype without the ecm fairings this week that had me wondering if it wasn't an old picture but in fact a J-10C prototype.