You may recall that Wolfenstein: The New Order, which came out in March of 2014, offered access to the Doom beta test (which, to be clear, hasn't yet happened) as a preorder bonus. As it turns out, there's something of a second bonus on offer to those who preordered: The opportunity to sign up for the Doom multiplayer alpha test.
The Doom multiplayer alpha "is a series of development-driven tests designed to stress test the game’s dedicated server infrastructure in a real-world consumer environment," as it's described at Doom.com. It will feature a single map, the industrial-themed Heatwave, one game mode (6v6 Team Deathmatch), one demon transformation type, and one "power weapon." More conventionally, it will also offer a limited arsenal of six weapons and two equippable items. Registrations, however, are limited to those who purchased Wolfenstein: The New Order on or before May 26, 2014.
"Our alphas will be closed and limited to help us test infrastructure. We will only be pulling from the Wolf: TNO folks for our closed alphas, since there are more of those folks than we need for alpha tests," Bethesda's Pete Hines explained. "When we do the full beta (the one that Wolf: TNO folks are guaranteed to get into) we will have more info on whether any wider audience can join in."
Chris got some hands-on time with Doom at this year's QuakeCon, which you can dig into here. It sounds promising and also a good bit different than the original Doom, with melee combat, upgradeable weapons, and, in deathmatch mode at least, a two gun carry limit. Players will also, as mentioned above, be able to transform into demons through the use of an intermittently-spawning "demon rune," which promises to be a fun way to discover how the other half lives.
If you're eligible to take part in the alpha, you can sign by up selecting the PC option at the signup site, which leads to a prompt for either the access code that was included with Wolfenstein or a sign-in through Steam. There's no word on when the alpha testing will begin, but Doom is expected to launch in the spring of 2016.