diff -r 000000000000 -r 6474c204b198 testing/mochitest/tests/Harness_sanity/SpecialPowersLoadChromeScript.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/testing/mochitest/tests/Harness_sanity/SpecialPowersLoadChromeScript.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,11 @@
+// Just receive 'foo' message and forward it back
+// as 'bar' message
+addMessageListener("foo", function (message) {
+  sendAsyncMessage("bar", message);
+});
+
+addMessageListener("valid-assert", function (message) {
+  assert.ok(true, "valid assertion");
+  assert.equal(1, 1, "another valid assertion");
+  sendAsyncMessage("valid-assert-done");
+});