'The configuration hash changes when a new version is saved.'

def test_hash_on_save(self):

    path = FilePath(self.mktemp())
    service = ConfigurationPersistenceService(reactor, path)
    service.startService()
    self.addCleanup(service.stopService)
    original = self.get_hash(service)
    d = service.save(LATEST_TEST_DEPLOYMENT)
    def saved(_):
        updated = self.get_hash(service)
        self.assertNotEqual(updated, original)
    d.addCallback(saved)
    return d
