That's because py.test won't invoke the `setUp` method if they don't because that's how py.test's nose compatibility works it seems.

In the long run, I would like to replace `setUp` and `tearDown` with py.test style fixtures and probably get rid of a lot of classes too.

Right now I'm making py.test work but still letting nosetests work too.

Once people are comfortable with `py.test`, I want to break nosetests compatibility and make everything py.test style.