diff -r 000000000000 -r 6474c204b198 mobile/android/base/tests/testJNI.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mobile/android/base/tests/testJNI.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,27 @@
+// -*- Mode: js2; tab-width: 2; indent-tabs-mode: nil; js2-basic-offset: 2; js2-skip-preprocessor-directives: t; -*-
+/* 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/. */
+
+Components.utils.import("resource://gre/modules/ctypes.jsm");
+Components.utils.import("resource://gre/modules/JNI.jsm");
+
+add_task(function test_JNI() {
+  let iconSize = -1;
+
+  let jni = null;
+  try {
+    jni = new JNI();
+    let cls = jni.findClass("org/mozilla/gecko/GeckoAppShell");
+    let method = jni.getStaticMethodID(cls, "getPreferredIconSize", "()I");
+    iconSize = jni.callStaticIntMethod(cls, method);
+  } finally {
+    if (jni != null) {
+      jni.close();
+    }
+  }
+
+  do_check_neq(iconSize, -1);
+});
+
+run_next_test();