list.set(2, "C");
    assertEquals("b", tailIterator.next());
    assertEquals("C", tailIterator.next());
    assertFalse(tailIterator.hasNext());
  }

  public void testSkip_structurallyModifiedSkipSome() throws Exception {
    Collection<String> set = new LinkedHashSet<>(asList("a", "b", "c"));
    Iterable<String> tail = skip(set, 1);
    set.remove("b");
    set.addAll(newArrayList("A", "B", "C"));