To include helper on FactoryGirl

    FactoryGirl::SyntaxRunner.send(:include, FactoryHelpers)

To include on RSpec and configure for clear all variables after each spec

RSpec.configure do |config|
  config.include FactoryHelpers

  config.after(:each) do
    FactoryVariables.clear
  end
end

So, you can call instance_factory on FactoryGirl factories, or in RSpec.