How to unload fixtures data?

I've tried to unload fixture data by rolling back db:migration and
rolling forward, then reloading fixtures with rake db:fixtures:load.
Strangely, the previous fixture data loads, not the updated, error-
free fixture data. I don't know why this happens. I seem to remember a
rake command for unloading fixture data but can't remember the
operative word. Any help?

Carson