diff -r 000000000000 -r 6474c204b198 browser/devtools/markupview/test/browser_markupview_toggle_01.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/devtools/markupview/test/browser_markupview_toggle_01.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,45 @@
+/* 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 clicking on twisties
+
+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("Clicking on the UL parent expander, and waiting for children");
+  let onChildren = waitForChildrenUpdated(inspector);
+  let onUpdated = inspector.once("inspector-updated");
+  EventUtils.synthesizeMouseAtCenter(container.expander, {},
+    inspector.markup.doc.defaultView);
+  yield onChildren;
+  yield onUpdated;
+
+  info("Checking that child LI elements have been created");
+  for (let li of content.document.querySelectorAll("li")) {
+    ok(getContainerForRawNode(li, inspector),
+      "A container for the child LI element was created");
+  }
+  ok(container.expanded, "Parent UL container is expanded");
+
+  info("Clicking again on the UL expander");
+  // No need to wait, this is a local, synchronous operation where nodes are
+  // only hidden from the view, not destroyed
+  EventUtils.synthesizeMouseAtCenter(container.expander, {},
+    inspector.markup.doc.defaultView);
+
+  info("Checking that child LI elements have been hidden");
+  for (let li of content.document.querySelectorAll("li")) {
+    let liContainer = getContainerForRawNode(li, inspector);
+    is(liContainer.elt.getClientRects().length, 0,
+      "The container for the child LI element was hidden");
+  }
+  ok(!container.expanded, "Parent UL container is collapsed");
+});