assertEquals("c", itr2.next());
  }

  public void testConcatPartiallyAdvancedFirst() {
    Iterator<String> itr1 =
        Iterators.concat(Iterators.singletonIterator("a"), Iterators.forArray("b", "c"));
    assertEquals("a", itr1.next());
    assertEquals("b", itr1.next());
    Iterator<String> itr2 = Iterators.concat(itr1, Iterators.singletonIterator("d"));
    assertEquals("c", itr2.next());