### Question:
MutableLongDiffSetsImpl implements MutableLongDiffSets { @Override public boolean isEmpty() { return added.isEmpty() && removed.isEmpty(); } MutableLongDiffSetsImpl( MutableLongSet added, MutableLongSet removed, CollectionsFactory collectionsFactory );  MutableLongDiffSetsImpl( CollectionsFactory collectionsFactory ); @Override boolean isAdded( long element ); @Override boolean isRemoved( long element ); @Override void removeAll( LongIterable elements ); @Override void addAll( LongIterable elements ); @Override void add( long element ); @Override boolean remove( long element ); @Override LongIterator augment( LongIterator source ); @Override PrimitiveLongResourceIterator augment( PrimitiveLongResourceIterator source ); @Override int delta(); @Override LongSet getAdded(); @Override LongSet getRemoved(); @Override boolean isEmpty();  }### Answer:
@Test public void newDiffSetIsEmpty() { assertTrue( createDiffSet().isEmpty() ); }