The first public beta test for Halo 4 on PC through The Master Chief Collection was scheduled to take place last week, but Microsoft chose to delay it due to a “blocker” issue. Thankfully, this problem is expected to be sorted out in short order, and beta invitations should begin going out soon.
“Unfortunately, we’re not quite ready yet,” Halo’s community director, Brian Jarrard, wrote on the Halo forums. “As of this writing, the team has one remaining blocker to address before we can progress the build to Ring 3 and send out Halo Insider invites. We’re close and, assuming this blocker can get resolved quickly without any further issues, we’re hoping to kick things off next week.”
A “blocker” is a bug that is “severe” enough to stop the beta test from working as intended, developer 343 says. When this bug for Halo 4 is fixed, the team will get the client ready for testers. That being said, the beta version of Halo 4 may still contain bugs, since it is a work-in-progress version of the game, just not bugs that are as critical in nature.