gecko-dev/dom/base/test/test_treewalker_nextsibling.xml

<?xml-stylesheet type="text/css" href="/tests/SimpleTest/test.css" ?>
<root>
  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js" xmlns="http://www.w3.org/1999/xhtml"/>

  <body xmlns="http://www.w3.org/1999/xhtml">
    <p id="display"></p>
    <div id="content" style="display: none;"></div>
    <textarea id="test" style="height: 300px; max-width: 800px; overflow: scroll;"
              rows="10" cols="160" readonly="readonly"/>
  </body>

<pre id="test" xmlns="http://www.w3.org/1999/xhtml">
<script class="testbody" type="text/javascript" xmlns="http://www.w3.org/1999/xhtml">
<![CDATA[
var passedNodes = new WeakMap();
function setPass(aNode) {
  passedNodes.set(aNode, true);
}

SimpleTest.waitForExplicitFinish();

window.addEventListener("load", function() {
  const nsIDOMNodeFilter = SpecialPowers.Ci.nsIDOMNodeFilter;
  var walker = document.createTreeWalker(
    document,
    nsIDOMNodeFilter.SHOW_TEXT | nsIDOMNodeFilter.SHOW_DOCUMENT,
    null
  );
  setPass(walker.firstChild());
  while (walker.nextSibling()) {
    setPass(walker.currentNode);
  }

/*
From http://www.w3.org/TR/2000/REC-DOM-Level-2-Traversal-Range-20001113/traversal.html#Traversal-TreeWalker
Omitting nodes from the logical view of a subtree can result in a structure that
is substantially different from the same subtree in the complete, unfiltered
document. Nodes that are siblings in the TreeWalker view may be children of
different, widely separated nodes in the original view. For instance, consider a
NodeFilter that skips all nodes except for Text nodes and the root node of a
document. In the logical view that results, all text nodes will be siblings and
appear as direct children of the root node, no matter how deeply nested the
structure of the original document.
*/

  walker2 = document.createTreeWalker(document, nsIDOMNodeFilter.SHOW_TEXT, null);
  while (walker2.nextNode()) {
    var cNode = walker2.currentNode;
    ok(passedNodes.get(cNode), "Every text node should appear: " + walker2.currentNode.nodeValue);
    walker.currentNode = cNode;
    var parent = walker.parentNode();
    is(parent, document, "parent of text node should be document");

    // Check nextSibling's previousSibling.
    walker.currentNode = cNode;
    if (walker.nextSibling()) {
      is(cNode, walker.previousSibling(), "nextSibling.previousSibling should be consistent");
    }

    // Check previousSibling's nextSibling.
    walker.currentNode = cNode;
    if (walker.previousSibling()) {
      is(cNode, walker.nextSibling(), "previousSibling.nextSibling should be consistent");
    }
  }
  SimpleTest.finish();
}, true);
]]>
</script>
</pre>

  <test>
    zero
    <one>
      one-A
      <two>
        two-A
      </two>
      <two>
        two-B
      </two>
      one-B
    </one>
    <one>
      one-C
      <two>
        two-D
      </two>
      <two>
        two-E
      </two>
      one-F
    </one>
    zero
  </test>
</root>