<!doctype html>
<meta charset="utf-8">
<title>Do only fully active documents count for session history?</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<body>
  <iframe id="child"></iframe>
</body>
<script>
  async_test(function(t) {
    var old_history_len = window.history.length;
    var child = document.getElementById("child");
    var timer = window.setInterval(t.step_func(poll), 100);
    function poll() {
      if (child.getAttribute("data-child-loaded")) {
        // Check to see how many entries have been added to the session history.
        // The spec https://html.spec.whatwg.org/multipage/#joint-session-history
        // says that only fully active documents are included in the joint session history.
        // If only fully active documents count, then the only fully active document
        // is the child, with session length 1, so the joint session length change will be 1.
        // If all documents count, then the grandchild is reachable via the session history,
        // and it has session length 1, so the joint session length change will be 2.
        assert_equals(2, window.history.length - old_history_len);
        window.clearInterval(timer);
        t.done();
      }
    }
    child.src = "joint-session-history-child1.html";
  });
</script>
