'If a I{Host} header must be added to the request, the L{Headers}
instance passed to L{Agent.request} is not modified.'

def test_headersUnmodified(self):

    headers = http_headers.Headers()
    self.agent._getEndpoint = (lambda *args: self)
    self.agent.request('GET', 'http://example.com/foo', headers)
    protocol = self.protocol
    self.assertEqual(len(protocol.requests), 1)
    self.assertEqual(headers, http_headers.Headers())
