Some sample code to illustrate that current_user = foo doesn't set @current_user

sessions_helper.rb

def sign_in(user)
  cookies.permanent.signed[:remember_token] = [user.id, user.salt]
  current_user = user
  # self.current_user = user will work though

  raise "#sign_in --> @current_user is still nil" unless @current_user == user

  # gross hack; otherwise the method returns nil since raise would be last line
  user
end

def sign_out
  cookies.delete(:remember_token)
  current_user = nil
  # self.current_user = nil will work though

  raise "#sign_out --> @current_user isn't nil" unless @current_user == nil
end