In "Fixin' Fixtures" Chris Wanstrath looks at how to make working with fixtures in a Rails testing environment a lot less painful. His opening paragraph says it best:

The main problem with fixtures, for me, has always been how unfun they are. They literally suck the fun out of anything they’re around. You throw them in your test/ directory, then suddenly testing is, like, work. But it’s not work, dammit. This is Ruby, dammit.

So, keep them fun. Write your fixtures in Ruby.

Enjoy!