diff -r 000000000000 -r 6474c204b198 browser/devtools/markupview/test/browser_markupview_pagesize_02.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/devtools/markupview/test/browser_markupview_pagesize_02.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,46 @@
+/* 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";
+
+// Tests that the markup view loads only as many nodes as specified
+// by the devtools.markup.pagesize preference and that pressing the "show all nodes"
+// actually shows the nodes
+
+const TEST_URL = TEST_URL_ROOT + "doc_markup_pagesize_02.html";
+
+// Make sure nodes are hidden when there are more than 5 in a row
+Services.prefs.setIntPref("devtools.markup.pagesize", 5);
+
+let test = asyncTest(function*() {
+  let {inspector} = yield addTab(TEST_URL).then(openInspector);
+
+  info("Selecting the UL node");
+  yield clickContainer("ul", inspector);
+  info("Reloading the page with the UL node selected will expand its children");
+  yield reloadPage(inspector);
+  yield inspector.markup._waitForChildren();
+
+  info("Click on the 'show all nodes' button in the UL's list of children");
+  yield showAllNodes(inspector);
+
+  assertAllNodesAreVisible(inspector);
+});
+
+function showAllNodes(inspector) {
+  let container = getContainerForRawNode("ul", inspector);
+  let button = container.elt.querySelector("button");
+  ok(button, "All nodes button is here");
+  let win = button.ownerDocument.defaultView;
+
+  EventUtils.sendMouseEvent({type: "click"}, button, win);
+  return inspector.markup._waitForChildren();
+}
+
+function assertAllNodesAreVisible(inspector) {
+  let ul = getNode("ul");
+  let container = getContainerForRawNode(ul, inspector);
+  ok(!container.elt.querySelector("button"), "All nodes button isn't here anymore");
+  is(container.children.childNodes.length, ul.children.length);
+}