### Question:
ShortSet implements Serializable { public void add(short key) { if (!contains(key)) { addKnownAbsent(key); } } ShortSet(int capacity); void add(short key); void addAll(ShortSet that); void addKnownAbsent(short key); void clear(); boolean contains(short key); void copyDataFrom(ShortSet that); @Override boolean equals(Object obj); short get(int i); @Override int hashCode(); void remove(short key); void removeKnownPresent(int key); int size(); @Override String toString(); String toString(CoordinateSystem coords);  }### Answer:
@Test public void testAdd() { assertEquals(0, set.size()); set.add((short)23); set.add((short)99); set.add((short)99); assertEquals(2, set.size()); assertEquals(2, set.size()); assertTrue(set.contains((short)23)); assertFalse(set.contains((short)0)); }