From the official WOW forums the following piece of information has been stated about the start of Raid Testing:
[bluequote author=”Daelo” link=http://blue.mmo-champion.com/topic/227584-raid-testing-starting-soon/ source=http://us.battle.net/wow/en/forum/topic/5889160100#1]We plan to start Mists of Pandaria Beta raid testing this Friday, June 22. We’ll begin testing with the 10 player Normal difficulty version of the Stone Guard in Mogu’shan Palace. Available testing times for testing will be posted soon. 25 player Normal difficulty testing should begin next week, with Raid Finder and Heroic difficulty testing to follow in the weeks ahead.
You must be level 90 to participate in the raid test, and level 90 character templates will not initially be available. We do have some new technology that automatically raises or lowers your items to the appropriate level for testing. So as long as you have a Mists of Pandaria quest or dungeon item in every slot, you’ll be fine.
Note that player interface add-ons are disabled on the beta at this time while we work through some technical issues. They’ll be available once again at some point in the future.
As always with raid testing on beta or public test realms, the schedule is subject to change or cancellation with very little warning. Server issues, build issues, newly discovered encounter, combat, or class bugs, and many other reasons could prevent testing. While I will endeavor to provide warning about future tests, this will also not always be possible. Whatever I do know, I’ll post here in the Beta Dungeons forum as soon as possible.
I’m really looking forward to everyone’s feedback (it really does matter!), and my thanks to everyone who’s able to participate in the upcoming tests.[/bluequote]
What are your predicitons for MOP will raiding continue to shift towards 10 mans?