External Test Functions (Rails)

I have a method I am writing in test_helper.rb to simplify some bulk testing for HTML elements. While I am experimentally developing this function now, I would like to spin it off into its own stand-alone function. If this were application code, it would go in lib/ (I think?), but since it is test code, where would I put it? Is there an location for external code for tests or would I just create a new file/directory to hold my re-usable code and require it inside test_helper.rb?