### Question:
DataNode implements Record { public synchronized Set<String> getChildren() { if (children == null) { return EMPTY_SET; } return Collections.unmodifiableSet(children); } DataNode();  DataNode(byte[] data, Long acl, StatPersisted stat); synchronized boolean addChild(String child); synchronized boolean removeChild(String child); synchronized void setChildren(HashSet<String> children); synchronized Set<String> getChildren(); synchronized void copyStat(Stat to); synchronized void deserialize(InputArchive archive, String tag); synchronized void serialize(OutputArchive archive, String tag); boolean isDigestCached(); void setDigestCached(boolean digestCached); long getDigest(); void setDigest(long digest); synchronized byte[] getData(); public StatPersisted stat; }### Answer:
@Test public void testGetChildrenReturnsImmutableEmptySet() { DataNode dataNode = new DataNode(); Set<String> children = dataNode.getChildren(); try { children.add("new child"); fail("UnsupportedOperationException is expected"); } catch (UnsupportedOperationException e) { } }