diff -r 000000000000 -r 6474c204b198 content/base/test/unit/test_error_codes.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/content/base/test/unit/test_error_codes.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,63 @@
+/* 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/.
+ */
+
+var gExpectedStatus = null;
+var gNextTestFunc   = null;
+
+var asyncXHR = {
+  load: function() {
+    var request = Components.classes["@mozilla.org/xmlextras/xmlhttprequest;1"]
+                            .createInstance(Components.interfaces.nsIXMLHttpRequest);
+    request.open("GET", "http://localhost:4444/test_error_code.xml", true);
+
+    var self = this;
+    request.addEventListener("error", function(event) { self.onError(event); }, false);
+    request.send(null);
+  },
+  onError: function doAsyncRequest_onError(event) {
+    var request = event.target.channel.QueryInterface(Components.interfaces.nsIRequest);
+    do_check_eq(request.status, gExpectedStatus);
+    gNextTestFunc();
+  }
+}
+
+function run_test() {
+  do_test_pending();
+  do_timeout(0, run_test_pt1);
+}
+
+// network offline
+function run_test_pt1() {
+  var ioService = Components.classes["@mozilla.org/network/io-service;1"]
+                            .getService(Components.interfaces.nsIIOService);
+
+  try {
+    ioService.manageOfflineStatus = false;
+  }
+  catch (e) {
+  }
+  ioService.offline = true;
+
+  gExpectedStatus = Components.results.NS_ERROR_OFFLINE;
+  gNextTestFunc = run_test_pt2;
+  dump("Testing error returned by async XHR when the network is offline\n");
+  asyncXHR.load();
+}
+
+// connection refused
+function run_test_pt2() {
+  var ioService = Components.classes["@mozilla.org/network/io-service;1"]
+                            .getService(Components.interfaces.nsIIOService);
+  ioService.offline = false;
+
+  gExpectedStatus = Components.results.NS_ERROR_CONNECTION_REFUSED;
+  gNextTestFunc = end_test;
+  dump("Testing error returned by aync XHR when the connection is refused\n");
+  asyncXHR.load();
+}
+
+function end_test() {
+  do_test_finished();
+}