assertEqualCharNodes(traverser.depthFirstPostOrder('a'), "dbca");
    assertEqualCharNodes(traverser.depthFirstPostOrder('b'), "db");
    assertEqualCharNodes(traverser.depthFirstPostOrder('c'), "dbac");
    assertEqualCharNodes(traverser.depthFirstPostOrder('d'), "d");
  }

  @Test
  public void forGraph_depthFirstPostOrderIterable_multigraph() {

    assertEqualCharNodes(traverser.depthFirstPostOrder('a'), "dbca");
    assertEqualCharNodes(traverser.depthFirstPostOrder('b'), "db");
    assertEqualCharNodes(traverser.depthFirstPostOrder('c'), "dbac");
    assertEqualCharNodes(traverser.depthFirstPostOrder('d'), "d");
  }

  @Test
  public void forGraph_depthFirstPostOrderIterable_multigraph() {

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