diff -r 000000000000 -r 6474c204b198 browser/components/tabview/test/browser_tabview_bug634085.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/tabview/test/browser_tabview_bug634085.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,49 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function test() {
+  let numChildren = 7;
+
+  let assertTopOfStack = function (tabItem) {
+    ok(!tabItem.getHidden(), "tabItem is visible");
+    is(tabItem.zIndex, tabItem.parent.getZ() + numChildren + 1, "zIndex");
+  }
+
+  let testTopOfStack = function (tabItem, callback) {
+    hideTabView(function () {
+      gBrowser.selectedTab = tabItem.tab;
+
+      showTabView(function () {
+        assertTopOfStack(tabItem);
+        callback();
+      });
+    });
+  }
+
+  let finishTest = function () {
+    registerCleanupFunction(function () {
+      is(1, gBrowser.tabs.length, "there is one tab, only");
+      ok(!TabView.isVisible(), "tabview is not visible");
+    });
+
+    finish();
+  }
+
+  waitForExplicitFinish();
+
+  showTabView(function () {
+    let groupItem = createGroupItemWithBlankTabs(window, 150, 150, 10, numChildren);
+
+    registerCleanupFunction(function () {
+      closeGroupItem(groupItem, function () TabView.hide());
+    });
+
+    testTopOfStack(groupItem.getChild(1), function () {
+      testTopOfStack(groupItem.getChild(6), function () {
+        closeGroupItem(groupItem, function () {
+          hideTabView(finishTest);
+        });
+      });
+    });
+  });
+}