diff -r 000000000000 -r 6474c204b198 browser/components/tabview/test/browser_tabview_bug628887.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/tabview/test/browser_tabview_bug628887.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,50 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function test() {
+  waitForExplicitFinish();
+
+  newWindowWithTabView(function(win) {
+    registerCleanupFunction(function() win.close());
+
+    let cw = win.TabView.getContentWindow();
+    let groupItemOne = cw.GroupItems.groupItems[0];
+
+    let groupItemTwo = createGroupItemWithBlankTabs(win, 100, 100, 40, 2);
+    ok(groupItemTwo.isStacked(), "groupItem is now stacked");
+
+    is(win.gBrowser.tabs.length, 3, "There are three tabs");
+
+    // the focus should remain within the group after it's expanded
+    groupItemTwo.addSubscriber("expanded", function onExpanded() {
+      groupItemTwo.removeSubscriber("expanded", onExpanded);
+
+      ok(groupItemTwo.expanded, "groupItemTwo is expanded");
+      is(cw.UI.getActiveTab(), groupItemTwo.getChild(0),
+         "The first tab item in group item two is active in expanded mode");
+
+      EventUtils.synthesizeKey("VK_DOWN", {}, cw);
+      is(cw.UI.getActiveTab(), groupItemTwo.getChild(0),
+         "The first tab item is still active after pressing down key");
+
+      // the focus should goes to other group if the down arrow is pressed
+      groupItemTwo.addSubscriber("collapsed", function onExpanded() {
+        groupItemTwo.removeSubscriber("collapsed", onExpanded);
+
+        ok(!groupItemTwo.expanded, "groupItemTwo is not expanded");
+        is(cw.UI.getActiveTab(), groupItemTwo.getChild(0),
+           "The first tab item is active in group item two in collapsed mode");
+
+        EventUtils.synthesizeKey("VK_DOWN", {}, cw);
+        is(cw.UI.getActiveTab(), groupItemOne.getChild(0),
+           "The first tab item in group item one is active after pressing down key");
+
+        finish();
+      });
+
+      groupItemTwo.collapse();
+    });
+
+    groupItemTwo.expand();
+  });
+}