'Zeroes and negative values are not accepted in id range expressions. RFC
3501 states that sequence numbers and sequence ranges consist of
non-negative numbers (RFC 3501 section 9, the seq-number grammar item).'

def test_invalidIdListParserNonPositive(self):

    inputs = ['0:5', '0:0', '*:0', '0', '-3:5', '1:-2', '-1']
    for input in inputs:
        self.assertRaises(imap4.IllegalIdentifierError, imap4.parseIdList, input, 12345)
