diff -r 000000000000 -r 6474c204b198 browser/base/content/test/general/browser_bug623893.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/base/content/test/general/browser_bug623893.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,47 @@
+function test() {
+  waitForExplicitFinish();
+
+  loadAndWait("data:text/plain,1", function () {
+    loadAndWait("data:text/plain,2", function () {
+      loadAndWait("data:text/plain,3", runTests);
+    });
+  });
+}
+
+function runTests() {
+  duplicate(0, "maintained the original index", function () {
+    gBrowser.removeCurrentTab();
+
+    duplicate(-1, "went back", function () {
+      duplicate(1, "went forward", function () {
+        gBrowser.removeCurrentTab();
+        gBrowser.removeCurrentTab();
+        gBrowser.addTab();
+        gBrowser.removeCurrentTab();
+        finish();
+      });
+    });
+  });
+}
+
+function duplicate(delta, msg, cb) {
+  var start = gBrowser.sessionHistory.index;
+
+  duplicateTabIn(gBrowser.selectedTab, "tab", delta);
+  let tab = gBrowser.selectedTab;
+
+  tab.addEventListener("SSTabRestored", function tabRestoredListener() {
+    tab.removeEventListener("SSTabRestored", tabRestoredListener, false);
+    is(gBrowser.sessionHistory.index, start + delta, msg);
+    executeSoon(cb);
+  }, false);
+}
+
+function loadAndWait(url, cb) {
+  gBrowser.selectedBrowser.addEventListener("load", function () {
+    gBrowser.selectedBrowser.removeEventListener("load", arguments.callee, true);
+    executeSoon(cb);
+  }, true);
+
+  gBrowser.loadURI(url);
+}