Unfortunately, you can't rely on a response code of 200 always indicating success - some web servers (I've heard) return that code even for a failed request.

It turns out that I'm testing a web application that I'm maintaining -- so the application is well behaved in that regard. I check that the status was OK, and also check that the content is what I was expecting.

And I expect to get a 200 Status even on a page that returns something like 'User not found' -- that isn't a protocol error, it's an application error. I also expect to get a 404 on a 'page not found' error, but for pages that are part of a package that may not be installed, that's OK. What I think you're describing is conflating an application error with a protocol error, which I don't think is right.

And now I know to read the part of the module deltas that say something like "This may break your code" much more closely. :)