In spec/controller file not taking controller property

My rspec file is not taking controller property.

In controller instance variable defined as :

@portal_news=PortalNews.new

In rspec file my code is
get :create,:portal_news=>{:user_id=>101}
assigns[:portal_news].user_id.should=101

I getting error is

NoMethodError in ‘PortalNewsController should_check_variable’
undefined method `user_id’ for nil:NilClass

please post the solution.I am waiting for reply