### Question:
MutableKeySet extends AbstractKeySet<K> { @Override public void clear() { map().clear(); } MutableKeySet(final MutableTrieMap<K, ?> map); @Override Iterator<K> iterator(); @Override void clear(); @Override @SuppressWarnings("checkstyle:parameterName") boolean remove(final Object o);  }### Answer:
@Test public void testClear() { set.clear(); assertTrue(map.isEmpty()); assertTrue(set.isEmpty()); }