### Question:
EmptyIntSet extends AbstractImmutableIntSet { @Override public boolean isEmpty() { return true; }  static IntSet getInstance(); @Override boolean contains(int i); @Override boolean containsAll(IntSet set); @Override int size(); @Override boolean isEmpty(); @Override boolean contains(Object o); @Override PrimitiveIterator.OfInt iterator(); @Override Object[] toArray(); @Override T[] toArray(T[] a); @Override boolean containsAll(Collection<?> c); @Override IntStream intStream(); @Override boolean equals(Object obj); @Override String toString();  }### Answer:
@Test public void testIsEmpty() { assertTrue(es.isEmpty()); }