Load a fixture manually in setup?

I’m running into a problem where one of my fixtures uses ERb to get an
id for a row that isn’t created yet. In setup, I create that row. Since
it appears that fixtures are loaded before setup is run, that’s a

I can’t put the row creation in a fixture - its part of the business
rules of one of my models.

Anyone know how to load a fixture manually at a specific time?