### Question:
LinkedListIndexedCollection extends Collection { @Override public void add(Object value) { Objects.requireNonNull(value); if (first == null) { first = last = new ListNode(null, null, value); } else { last.next = new ListNode(last, null, value); last = last.next; } ++size; } LinkedListIndexedCollection();  LinkedListIndexedCollection(Collection other); @Override int size(); @Override boolean contains(Object value); @Override boolean remove(Object value); @Override Object[] toArray(); @Override void forEach(Processor processor); @Override void add(Object value); Object get(int index); @Override void clear(); void insert(Object value, int position); int indexOf(Object value); void remove(int index); @Override String toString(); static final int VALUE_NOT_FOUND_RETURN_VALUE; }### Answer:
@Test void testAddWithNull() { assertThrows(NullPointerException.class, () -> createCollectionWithNElements(0).add(null)); }