def test_defaultKnownHosts(self):
        """
        L{_NewConnectionHelper._knownHosts} is used to create a
        L{KnownHostsFile} if one is not passed to the initializer.
        """
        result = object()
        self.patch(_NewConnectionHelper, '_knownHosts', lambda cls: result)

        helper = _NewConnectionHelper(
            None, None, None, None, None, None, None, None, None, None)

        self.assertIs(result, helper.knownHosts)

        L{_NewConnectionHelper._knownHosts} is used to create a
        L{KnownHostsFile} if one is not passed to the initializer.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_endpoints.py