Object toKeyValue = sm.get(toKey);
SortedMap sub = sm.subMap(fromKey, toKey);
int size = sm.size();
assertEquals(3, sub.size());
sub.clear();
assertEquals(0, sub.size());
assertEquals(size - 3, sm.size());
assertEquals(size - 3, sm.inverseBidiMap().size());
assertEquals(false, sm.containsKey(fromKey));