Setting headers in TestRequest

Hi. I'm using HTTP Basic auth for some of my REST interfaces, so I
want to run tests setting the HTTP AUTHORIZATION header. But I can't
find a way to do it in the functional test. I can see the response
headers in @response.headers, but there's no analogous hash in
@request.

Any hints?

Also, I can't find any API documentation for
ActionController::TestRequest -- anybody know where that's hiding?

Thanks!
Rod