Kaivax, a WoW forum community manager, revealed that WoW Classic's class design, battleground mechanics and stats on existing items will be set to their 1.12 state, despite the game releasing content that expands beyond that. This removes "progressive itemization," so if the stats on a specific piece of equipment was changed during the original updates, that won't take effect in this version.
Along with revealing the WoW Classic release date, Blizzard also listed plans for both a beta and stress test of the game. Players who opt-in for the testing on their account manager page and have an active subscription will be randomly selected for the beta starting May 15. Then the developer will have three stress tests where players can log in to play the game for a short period of time on the following dates: