diff -r 000000000000 -r 6474c204b198 browser/base/content/test/general/browser_selectTabAtIndex.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/base/content/test/general/browser_selectTabAtIndex.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,19 @@
+function test() {
+  for (let i = 0; i < 9; i++)
+    gBrowser.addTab();
+
+  var isLinux = navigator.platform.indexOf("Linux") == 0;
+  for (let i = 9; i >= 1; i--) {
+    EventUtils.synthesizeKey(i.toString(), { altKey: isLinux, accelKey: !isLinux });
+
+    is(gBrowser.tabContainer.selectedIndex, (i == 9 ? gBrowser.tabs.length : i) - 1,
+       (isLinux ? "Alt" : "Accel") + "+" + i + " selects expected tab");
+  }
+
+  gBrowser.selectTabAtIndex(-3);
+  is(gBrowser.tabContainer.selectedIndex, gBrowser.tabs.length - 3,
+     "gBrowser.selectTabAtIndex(-3) selects expected tab");
+
+  for (let i = 0; i < 9; i++)
+    gBrowser.removeCurrentTab();
+}