docshell/test/navigation/file_bug534178.html

<html>
  <head>
    <script>
    
      function testDone() {
        document.body.removeChild(document.body.firstChild);
        netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
        var isOK = false;
        try {
          isOK = history.previous != location;
        } catch(ex) {
          // history.previous should throw if this is the first page in shistory.
          isOK = true;
        }
        document.body.textContent = isOK ? "PASSED" : "FAILED";
        opener.ok(isOK, "Duplicate session history transactions should have been removed!");
        opener.nextTest();
        window.close();
      }
      function ifrload() {
        setTimeout(testDone, 0);
      }
      function test() {
        var ifr = document.getElementsByTagName("iframe")[0];
        ifr.onload = ifrload;
        ifr.src = "data:text/html,doc2";
      }
    </script>
  </head>
  <body onload="setTimeout(test, 0)"><iframe src="data:text/html,doc1"></iframe>
  </body>
</html>