Blizzard has posted some behind-the-scenes information on the development of WoW's PTR cycle and how upcoming raid testing is announced!
Blizzard This is super fair feedback and something we’ve talked about previously. To understand the problem, we need to take a step back and talk about how we do PTR testing:The week prior to a PTR test, we confirm which bosses are ready for testing and ask their designers to have them in a stable & testable state by the end of the week. Read more on wowhead.com