diff -r 000000000000 -r 6474c204b198 dom/payment/tests/unit/header_helper.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/payment/tests/unit/header_helper.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,38 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
+
+let subscriptLoader = Cc["@mozilla.org/moz/jssubscript-loader;1"]
+                        .getService(Ci.mozIJSSubScriptLoader);
+
+/**
+ * Start a new payment module.
+ *
+ * @param custom_ns
+ *        Namespace with symbols to be injected into the new payment module
+ *        namespace.
+ *
+ * @return an object that represents the payment module's namespace.
+ */
+function newPaymentModule(custom_ns) {
+  let payment_ns = {
+    importScripts: function fakeImportScripts() {
+      Array.slice(arguments).forEach(function (script) {
+        subscriptLoader.loadSubScript("resource://gre/modules/" + script, this);
+      }, this);
+    },
+  };
+
+  // Copy the custom definitions over.
+  for (let key in custom_ns) {
+    payment_ns[key] = custom_ns[key];
+  }
+
+  // Load the payment module itself.
+  payment_ns.importScripts("Payment.jsm");
+
+  return payment_ns;
+}