'``Configuration.applications`` raises a
``ConfigurationError`` if the application_configuration has a port
entry that is missing the internal port.'

def test_ports_missing_external(self):

    config = dict(version=1, applications={u'mysql-hybridcluster': dict(image=u'busybox', ports=[{u'internal': 90}])})
    parser = FlockerConfiguration(config)
    exception = self.assertRaises(ConfigurationError, parser.applications)
    self.assertEqual(u"Application    'mysql-hybridcluster'    has    a    config    error.    Invalid    ports    specification.    Missing    external    port.", exception.message)
