'Helper for unit tests for L{endpoints._SystemdParser.parseStreamServer}
for different address families.
Handling of the address family given will be verify.  If there is a
problem a test-failing exception will be raised.
@param addressFamily: An address family constant, like
L{socket.AF_INET}.
@param addressFamilyString: A string which should be recognized by the
parser as representing C{addressFamily}.'

def _parseStreamServerTest(self, addressFamily, addressFamilyString):

    reactor = object()
    descriptors = [5, 6, 7, 8, 9]
    index = 3
    parser = self._parserClass()
    parser._sddaemon = ListenFDs(descriptors)
    server = parser.parseStreamServer(reactor, domain=addressFamilyString, index=str(index))
    self.assertIs(server.reactor, reactor)
    self.assertEqual(server.addressFamily, addressFamily)
    self.assertEqual(server.fileno, descriptors[index])
