### Question:
LinkedBinaryTree extends AbstractBinaryTree<E> { @Override public int size() { return size; } LinkedBinaryTree(); @Override int size(); @Override Position<E> root(); @Override Position<E> parent(Position<E> p); @Override Position<E> left(Position<E> p); @Override Position<E> right(Position<E> p); Position<E> addRoot(E e); void insert(E e); Position<E> addLeft(Position<E> p, E e); Position<E> addRight(Position<E> p, E e); E set(Position<E> p, E e); void attach(Position<E> p, LinkedBinaryTree<E> t1,
                    LinkedBinaryTree<E> t2); E remove(Position<E> p); String toString(); static void main(String [] args);  }### Answer:
@Test void testSize() { LinkedBinaryTree<Integer> bt = new LinkedBinaryTree<Integer>(); Position<Integer> root = bt.addRoot(1); assertEquals(1, bt.size()); Position<Integer> l = bt.addLeft(root, 2); bt.remove(bt.root()); assertEquals(1, bt.size()); }