I don't think that this is much that problem since we don't test the HttpFoundation component. Therefore, I see no problem in relying on the status code constants. But, if you think it's clearer to the raw status code, I won't object in reverting this. I think it's more a matter of taste. :)

If we want to revert this, we must keep an eye on the ``book/testing.rst`` file, too. Then, would you like to do that or do you want me to create a separate pull request?