### Question:
WrappedBinaryNode implements BinaryTreeNode<E> { @Override public int getNumberOfChildren() { return delegateNode.getNumberOfChildren(); } WrappedBinaryNode(MutableBinaryTreeNode<E> node); @Override BinaryTreeNode<E> getLeft(); @Override BinaryTreeNode<E> getRight(); @Override Iterator<? extends BinaryTreeNode<E>> childStructuralIterator(); @Override BinaryTreeNode<E> getChild(int nChild); @Override E getElement(); @Override int getNumberOfChildren(); @Override Iterator<? extends BinaryTreeNode<E>> childIterator();  }### Answer:
@Test public void numberOfChildren() { final WrappedBinaryNode<String> wrappedParent = new WrappedBinaryNode<>(parent); assertEquals(2, wrappedParent.getNumberOfChildren()); }