'If the start byte position is omitted but the end byte position is
supplied, then the range is treated as requesting the last -N bytes of
the resource, where N is the end byte position.'

def test_implicitStart(self):

    self.request.requestHeaders.addRawHeader('range', 'bytes=-17')
    self.resource.render(self.request)
    self.assertEqual(''.join(self.request.written), self.payload[(-17):])
    self.assertEqual(len(''.join(self.request.written)), 17)
    self.assertEqual(self.request.responseCode, http.PARTIAL_CONTENT)
    self.assertEqual(self.request.responseHeaders.getRawHeaders('content-range')[0], 'bytes    47-63/64')
    self.assertEqual(self.request.responseHeaders.getRawHeaders('content-length')[0], '17')
