diff -r 000000000000 -r 6474c204b198 browser/metro/base/tests/mochitest/browser_sessionstore.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/metro/base/tests/mochitest/browser_sessionstore.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,55 @@
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+var gSessionStore = Cc["@mozilla.org/browser/sessionstore;1"]
+                    .getService(Ci.nsISessionStore);
+
+function test() {
+  runTests();
+}
+
+function getState() {
+  return JSON.parse(gSessionStore.getBrowserState());
+}
+
+function getTabData() {
+  return getState().windows[0].tabs;
+}
+
+function isValidTabData(aData) {
+  return aData && aData.entries && aData.entries.length &&
+           typeof aData.index == "number";
+}
+
+gTests.push({
+  desc: "getBrowserState tests",
+  run: function() {
+    // Wait for Session Manager to be initialized.
+    yield waitForCondition(() => window.__SSID);
+    info(window.__SSID);
+    let tabData1 = getTabData();
+    ok(tabData1.every(isValidTabData), "Tab data starts out valid");
+
+    // Open a tab.
+    let tab = Browser.addTab("about:mozilla");
+    let tabData2 = getTabData();
+    is(tabData2.length, tabData1.length, "New tab not added yet.");
+
+    // Wait for the tab's session data to be initialized.
+    yield waitForMessage("Content:SessionHistory", tab.browser.messageManager);
+    yield waitForMs(0);
+    let tabData3 = getTabData();
+    is(tabData3.length, tabData1.length + 1, "New tab added.");
+    ok(tabData3.every(isValidTabData), "Tab data still valid");
+
+    // Close the tab.
+    Browser.closeTab(tab, { forceClose: true } );
+    let tabData4 = getTabData();
+    is(tabData4.length, tabData1.length, "Closed tab removed.");
+    ok(tabData4.every(isValidTabData), "Tab data valid again");
+  }
+});