To include helper on FactoryGirl

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

To include on RSpec

RSpec.configure do |config|
  config.include InstanceFactory

  config.after(:each) do
    instance_factory_clear!
  end
end

To include on default test of rails 4

class ActiveSupport::TestCase
  include InstanceFactory
end

before :each do
  instance_factory_clear!
end

So, you can call instance_factory on FactoryGirl, RSpec, Minitest, or another.