diff -r 000000000000 -r 6474c204b198 browser/devtools/markupview/test/browser_markupview_toggle_03.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/devtools/markupview/test/browser_markupview_toggle_03.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,44 @@
+/* vim: set ts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+ http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// Test toggling (expand/collapse) elements by alt-clicking on twisties, which
+// should expand all the descendants
+
+const TEST_URL = TEST_URL_ROOT + "doc_markup_toggle.html";
+
+let test = asyncTest(function*() {
+  let {inspector} = yield addTab(TEST_URL).then(openInspector);
+
+  info("Getting the container for the UL parent element");
+  let container = getContainerForRawNode("ul", inspector);
+
+  info("Alt-clicking on the UL parent expander, and waiting for children");
+  let onUpdated = inspector.once("inspector-updated");
+  EventUtils.synthesizeMouseAtCenter(container.expander, {altKey: true},
+    inspector.markup.doc.defaultView);
+  yield onUpdated;
+  yield waitForMultipleChildrenUpdates(inspector);
+
+  info("Checking that all nodes exist and are expanded");
+  for (let node of content.document.querySelectorAll("ul, li, span, em")) {
+    let nodeContainer = getContainerForRawNode(node, inspector);
+    ok(nodeContainer, "Container for node " + node.tagName + " exists");
+    ok(nodeContainer.expanded,
+      "Container for node " + node.tagName + " is expanded");
+  }
+});
+
+// The expand all operation of the markup-view calls itself recursively and
+// there's not one event we can wait for to know when it's done
+function* waitForMultipleChildrenUpdates(inspector) {
+  // As long as child updates are queued up while we wait for an update already
+  // wait again
+  if (inspector.markup._queuedChildUpdates &&
+      inspector.markup._queuedChildUpdates.size) {
+    yield waitForChildrenUpdated(inspector);
+    return yield waitForMultipleChildrenUpdates(inspector);
+  }
+}
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