diff -r 000000000000 -r 6474c204b198 browser/components/sessionstore/test/unit/test_startup_session_async.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/sessionstore/test/unit/test_startup_session_async.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,27 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+
+// Test nsISessionStartup.sessionType in the following scenario:
+// - valid sessionstore.js;
+// - valid sessionCheckpoints.json with all checkpoints;
+// - the session store has been loaded
+
+function run_test() {
+  let profd = do_get_profile();
+
+  let sourceSession = do_get_file("data/sessionstore_valid.js");
+  sourceSession.copyTo(profd, "sessionstore.js");
+
+  let sourceCheckpoints = do_get_file("data/sessionCheckpoints_all.json");
+  sourceCheckpoints.copyTo(profd, "sessionCheckpoints.json");
+
+  do_test_pending();
+  let startup = Cc["@mozilla.org/browser/sessionstartup;1"].
+    getService(Ci.nsISessionStartup);
+
+  afterSessionStartupInitialization(function cb() {
+    do_check_eq(startup.sessionType, Ci.nsISessionStartup.DEFER_SESSION);
+    do_test_finished();
+  });
+}