Full information found here:
I have this same issue with TestUnit. Using Guard, Spork, Capybara, Test::Unit on Rails 3.1.3
Also have this issue. Using spork, capybara, and factory_girl_rails 1.6.0 on rails 3.1.3
Find my solution here: http://railsgotchas.wordpress.com/2012/01/31/activeadmin-spork-and-the-infamous-undefined-local-variable-or-method-view_factory/
Man it works !! That's really awesome ! Thanks !
The solution isn't working anymore, see: activeadmin/activeadmin#918