Iterable<Character> result = Traverser.forTree(TWO_TREES).breadthFirst('a');

    assertEqualCharNodes(result, "ab");
  }

  @Test
  public void forTree_breadthFirstIterable_twoTrees() {
    assertEqualCharNodes(Traverser.forTree(TWO_TREES).breadthFirst(charactersOf("a")), "ab");
    assertEqualCharNodes(Traverser.forTree(TWO_TREES).breadthFirst(charactersOf("ca")), "cadb");
  }