docshell/test/chrome/test_private_hidden_window.html

<!DOCTYPE HTML>
<html>
<!--
https://bugzilla.mozilla.org/show_bug.cgi?id=829383
-->
<head>
  <title>Test for Bug 829383</title>
  <script type="text/javascript" src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
  <link rel="stylesheet" type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css" />
</head>
<body>
<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=829383">Mozilla Bug 829383</a>
<p id="display"></p>
<div id="content" style="display: none">
  <iframe name="target"></iframe>
</div>
<pre id="test">
<script class="testbody" type="text/javascript">

SimpleTest.waitForExplicitFinish();
const Ci = Components.interfaces;
var mainWindow = window.QueryInterface(Ci.nsIInterfaceRequestor)
                       .getInterface(Ci.nsIWebNavigation)
                       .QueryInterface(Ci.nsIDocShellTreeItem)
                       .rootTreeItem
                       .QueryInterface(Ci.nsIInterfaceRequestor)
                       .getInterface(Ci.nsIDOMWindow);

// We need to wait for the hidden window to load, but can't access
// an event target for a regular event listener.
var hidden = mainWindow.Services.appShell.hiddenPrivateDOMWindow;
mainWindow.PrivateBrowsingUtils.whenHiddenPrivateWindowReady(function(hidden) {
  var iframe = hidden.document.createElement('iframe');
  iframe.src = 'generic.html';
  hidden.document.body.appendChild(iframe);

  var win = mainWindow.OpenBrowserWindow({private: true});
  win.addEventListener("load", function onLoad() {
    win.removeEventListener("load", onLoad, false);
    win.close();
    win = null;
  }, false);
});

function observer(aSubject, aTopic, aData) {
  is(aTopic, "last-pb-context-exited", "Unexpected observer topic");
  mainWindow.Services.obs.removeObserver(observer, "last-pb-context-exited");
  SimpleTest.finish();
}
mainWindow.Services.obs.addObserver(observer, "last-pb-context-exited", false);

</script>
</pre>
</body>
</html>