Senthil: Almost, but not quite. end_headers() needs to be called even if send_header() isn't called (though it may be being called behind the scenes, that's not necessarily obvious to a user).

In my original unit-testing code, I had only

request.send_response(200)

and that caused a failure. My code now has to read

request.send_response(200)
request.end_headers()

No send_header() in sight! Perhaps the end_header() call requirement should also be mentioned in the docs on send_response().