A few more tests that would be good:
* Check that if you have an action that attaches an `onDoneEnumerating` callback to the body enumerator, that that callback gets executed (this is important to ensure that the enumerator is consumed so any resources created for it get cleaned up, eg that files get closed etc).
* Check that for chunked responses, the chunked transfer encoding header is set, and the content length header is not set.
* Check that for actions that explicitly set a content length header, this header is passed as is, regardless of how much content is actually sent.
* Check that for actions that send an enumerator with multiple chunks, the content length header is not set, rather the transfer encoding header is set to chunked.