Besides the rumor of WS-15 testing on J-11,
- On being questioned about it, a senior military leader threw a counter question at the reporter "How do you know it has not been tested yet?". I can't seem to remember the name but I'm fairly certain it's about WS-15 on J-20.
I believe that was regarding TVC for J-20, and was concluded to likely refer to a TVC variant of WS-10 rather than WS-15. That was in 2018 at Zhuhai.
I dont think that anyone here knows for certain if WS-15 has been test-flighted or not. But people here keep saying that it must have been already tested-flighted. Based on what?
The rumour about WS-15 having been flight tested was from a couple of years ago from Shi Lao, but obviously everyone treats any rumours about WS-15 with great caution even if they are considered to be quite credible.
The people who speak of it as if it is definitively confirmed or "must have been" already flight tested are overreaching a bit, because at the end of the day we don't have the evidence to make that kind of definitive claim.
But at the same time, for the purposes of discussion and trying to project things, it's far from unreasonable to say it probably has been test flown, until we have more definitive evidence (which may be in retrospect).