Greetings!
Dragonflight Season 4 dungeon testing begins on PTR realms today. The test period will begin today, Tuesday March 26, and end Monday April 1 at 10:00 a.m. PDT (13:00 EDT, 18:00 CEST). Please note that the test period may be adjusted in the event of technical difficulties.
The following dungeons are available for testing on Heroic, Mythic, and Mythic+ difficulty with the new dungeon progression update:

The Azure Vault
Brackenhide Hollow
Ruby Life Pools
Halls of Infusion
Algeth’ar Academy
The Nokhud Offensive
Neltharus
Uldaman, Legacy of Tyr

During the test period you’ll be able to acquire and customize Mythic Keystones by talking to the Keystone Vendor in Stormwind or Orgrimmar, and the nearby Dungeon Teleports NPC will assist you with transportation.
We look forward to hearing your feedback!