diff -r 000000000000 -r 6474c204b198 dom/mobilemessage/tests/marionette/test_thread_subject.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/mobilemessage/tests/marionette/test_thread_subject.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,67 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+MARIONETTE_TIMEOUT = 60000;
+MARIONETTE_HEAD_JS = 'head.js';
+
+const PHONE_NUMBER = "+1234567890";
+
+// Have a long long subject causes the send fails, so we don't need
+// networking here.
+const MMS_MAX_LENGTH_SUBJECT = 40;
+function genMmsSubject(sep) {
+  return "Hello " + (new Array(MMS_MAX_LENGTH_SUBJECT).join(sep)) + " World!";
+}
+
+function testSms(aProgressStr, aText) {
+  log("Testing thread subject: " + aProgressStr);
+
+  return sendSmsWithSuccess(PHONE_NUMBER, aText)
+    .then(function(message) {
+      log("  SMS sent, retrieving thread of id " + message.threadId);
+      return getThreadById(message.threadId);
+    })
+    .then(function(thread) {
+      log("  Got thread.lastMessageSubject = '" + thread.lastMessageSubject + "'");
+      is(thread.lastMessageSubject, "", "thread.lastMessageSubject");
+    });
+}
+
+function testMms(aProgressStr, aSubject) {
+  log("Testing thread subject: " + aProgressStr);
+
+  let mmsParameters = {
+    receivers: [PHONE_NUMBER],
+    subject: aSubject,
+    attachments: [],
+  };
+
+  // We use a long long message subject so it will always fail.
+  return sendMmsWithFailure(mmsParameters)
+    .then(function(result) {
+      log("  MMS sent, retrieving thread of id " + result.message.threadId);
+      return getThreadById(result.message.threadId);
+    })
+    .then(function(thread) {
+      log("  Got thread.lastMessageSubject = '" + thread.lastMessageSubject + "'");
+      is(thread.lastMessageSubject, aSubject, "thread.lastMessageSubject");
+    });
+}
+
+startTestCommon(function testCaseMain() {
+  return testSms("SMS", "text")
+    .then(testMms.bind(null, "SMS..MMS", genMmsSubject(" ")))
+    .then(testSms.bind(null, "SMS..MMS..SMS", "text"))
+    .then(deleteAllMessages)
+    .then(testMms.bind(null, "MMS", genMmsSubject(" ")))
+    .then(testSms.bind(null, "MMS..SMS", "text"))
+    .then(testMms.bind(null, "MMS..SMS..MMS", genMmsSubject(" ")))
+    .then(deleteAllMessages)
+    .then(testSms.bind(null, "SMS", "1"))
+    .then(testSms.bind(null, "SMS..SMS", "2"))
+    .then(testSms.bind(null, "SMS..SMS..SMS", "3"))
+    .then(deleteAllMessages)
+    .then(testMms.bind(null, "MMS", genMmsSubject("a")))
+    .then(testMms.bind(null, "MMS..MMS", genMmsSubject("b")))
+    .then(testMms.bind(null, "MMS..MMS..MMS", genMmsSubject("c")));
+});