diff -r 000000000000 -r 6474c204b198 xpcom/tests/unit/test_mac_bundle.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/tests/unit/test_mac_bundle.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,17 @@
+function run_test() { 
+  // this is a hack to skip the rest of the code on non-Mac platforms, 
+  // since #ifdef is not available to xpcshell tests...
+  if (!("nsILocalFileMac" in Components.interfaces))
+    return;
+  
+  // OK, here's the real part of the test:
+  // make sure these two test bundles are recognized as bundles (or "packages") 
+  var keynoteBundle = do_get_file("data/presentation.key");
+  var appBundle = do_get_file("data/SmallApp.app");
+  
+  do_check_true(keynoteBundle instanceof Components.interfaces.nsILocalFileMac);
+  do_check_true(appBundle instanceof Components.interfaces.nsILocalFileMac);
+  
+  do_check_true(keynoteBundle.isPackage());
+  do_check_true(appBundle.isPackage());
+}