There has been a leaked video from the opening scenes of the upcoming Halo: Reach beta test. The video, which is posted below, shows that there's multiplayer and single-player modes included in the test.
The short greeting message at the start confirms that the beta will give players an early look at a few levels from Halo: Reach.
“Welcome to the Halo: Reach Public Beta, the experience you are about to enjoy is an early sample of a few multiplayer and single-player levels from Halo: Reach, launching exclusively on Xbox 360 later this year. Until then, drive into Activities or Campaign and have a blast.”
Access to the beta is granted to those that purchased a copy of Halo 3: ODST.