autotest + test unit + rcov examples?

I'm having a hard time finding any examples of the right way to use
rcov with autotest and test unit under rails. I can't find a single
blog post that covers this.

In particular examples of what you put in .autotest would be very helpful.

Chris

Now I see why people probably don't use rcov with rails. It's
heuristics don't seem to be compatible. I have one unit test that's
just does a simple assert, yet rcov thinks 19% of my code is covered
(over 100 models and 20+ classes in lib). You can't avoid loading
most of your classes in rails, yet the simple act of loading the
classes means rcov thinks a lot of it is 'covered'.

So what are people using to measure code coverage in rails?

Chris