### Question:
NodeToElementWalker implements Walker<N> { @Override public void onCompleted() { delegateWalker.onCompleted(); } NodeToElementWalker(Walker<E> delegateWalker); @Override void onEmpty(); @Override boolean onNext(N node); @Override void onCompleted();  }### Answer:
@Test public void onCompleted() { final NodeToElementWalker<String, MutableSettableStructuredNode<String>> elementWalker = new NodeToElementWalker<>(walker); elementWalker.onCompleted(); Mockito.verify(walker).onCompleted(); }