assertEqualCharNodes(traverser.breadthFirst(charactersOf("dc")), "dcab");
    assertEqualCharNodes(traverser.breadthFirst(charactersOf("bc")), "bcda");
  }

  @Test
  public void forGraph_breadthFirst_tree() throws Exception {
    Traverser<Character> traverser = Traverser.forGraph(TREE);

    assertEqualCharNodes(traverser.breadthFirst('h'), "hdegabcf");
    assertEqualCharNodes(traverser.breadthFirst('d'), "dabc");