### Question:
GroupElement extends Element { public Set getMemberKeys() { return (Set) getObjectValue(); } GroupElement(Object key);  GroupElement(Object key, Object value, long version,
            long creationTime, long lastAccessTime, long nextToLastAccessTime,
            long lastUpdateTime, long hitCount); Set getMemberKeys(); static final String MASTER_GROUP_KEY; }### Answer:
@Test public void testConstructor() { GroupElement element = new GroupElement("key"); assertEquals("key", element.getKey()); assertNotNull(element.getObjectValue()); assertTrue(element.getObjectValue() instanceof Set); assertEquals(0, ((Set) element.getValue()).size()); assertNotNull(element.getMemberKeys()); assertEquals(0, element.getMemberKeys().size()); assertEquals(0L, element.getVersion()); long now = System.currentTimeMillis(); long MARGIN = 2000L; assertTrue(element.getCreationTime()-now<MARGIN); assertEquals(0L, element.getLastAccessTime()); assertEquals(0L, element.getNextToLastAccessTime()); assertEquals(0L, element.getLastUpdateTime()); assertEquals(0L, element.getHitCount()); }