public static HazelcastInstance getOrCreateHazelcastClient() {
        return getOrCreateClientInternal(null);
    }
@Test
    public void testGetOrCreateHazelcastClient_returnsSame_withNoConfig() {
        String hzConfigProperty = System.getProperty(CLIENT_CONFIG_PROP_NAME);
        try {
            System.setProperty(CLIENT_CONFIG_PROP_NAME, "classpath:hazelcast-client-test.xml");
            HazelcastInstance client1 = HazelcastClient.getOrCreateHazelcastClient();
            HazelcastInstance client2 = HazelcastClient.getOrCreateHazelcastClient();
            assertEquals("Calling two times getOrCreateHazelcastClient should return same client", client1, client2);
        } finally {
            if (hzConfigProperty == null) {
                System.clearProperty(CLIENT_CONFIG_PROP_NAME);
            } else {
                System.setProperty(CLIENT_CONFIG_PROP_NAME, hzConfigProperty);
            }
        }
    }