public Set<String> keySet() {
        return keys;
    }
@Test
    public void testKeySet_whenPropertiesAvailable() {
        Properties props = new Properties();
        props.setProperty("key1", "value1");
        props.setProperty("key2", "value2");
        HazelcastProperties properties = new HazelcastProperties(props);

        assertEquals(props.keySet(), properties.keySet());
    }