size.py

from httplib.HTTPConnection
from urlparse import urlparse

def get_size_of_page(url):
  o = urlparse(url)
  conn = HTTPConnection(o.netloc)
  conn.request("HEAD", o.path)
  resp = conn.getresponse()
  if resp.status == 200:
    return long(resp.getheader("Content-Lenght"))
  else:
    return None

size_test.py

import size

def test_should_get_size_of_page():
  # How would I mock HTTPConnection
  pass