'L{FileAuthority} lookup methods errback with L{DomainError} if
the requested C{name} shares a common suffix with its zone but
is not actually a descendant of its zone, in terms of its
sequence of DNS name labels. eg www.the-example.com has
nothing to do with the zone example.com.'

def test_domainErrorForNameWithCommonSuffix(self):

    testDomain = test_domain_com
    testDomainName = ('nonexistent.prefix-' + testDomain.soa[0])
    f = self.failureResultOf(testDomain.lookupAddress(testDomainName))
    self.assertIsInstance(f.value, DomainError)
