To make sure that your models are valid you can automatically test all of your factories with the following code

factory_girl_spec.rb

require 'spec_helper'

describe 'validate FactoryGirl factories' do
  FactoryGirl.factories.each do |factory|

    context "with factory for :#{factory.name}" do
      subject { FactoryGirl.build(factory.name) }
      it "is valid" do
        is_valid = subject.valid?
        is_valid.should be_true, subject.errors.full_messages.join(',')
      end

    end
  end
end