How to create has_and_belongs_to_many associations in Factory girl

Factorygirl has since been updated and now includes callbacks to solve this problem. Take a look at http://robots.thoughtbot.com/post/254496652/aint-no-calla-back-girl for more info.

Here is the solution that works for me.

FactoryGirl.define do

  factory :company do
    #company attributes
  end

  factory :user do
   companies {[FactoryGirl.create(:company)]}
   #user attributes
  end

end

if you will need specific company you can use factory this way

company = FactoryGirl.create(:company, #{company attributes})
user = FactoryGirl.create(:user, :companies => [company])

Hope this will be helpful for somebody.