diff -r 000000000000 -r 6474c204b198 services/common/tests/unit/test_async_chain.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/services/common/tests/unit/test_async_chain.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,30 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+Cu.import("resource://services-common/async.js");
+
+function run_test() {
+  _("Chain a few async methods, making sure the 'this' object is correct.");
+
+  let methods = {
+    save: function(x, callback) {
+      this.x = x;
+      callback(x);
+    },
+    addX: function(x, callback) {
+      callback(x + this.x);
+    },
+    double: function(x, callback) {
+      callback(x * 2);
+    },
+    neg: function(x, callback) {
+      callback(-x);
+    }
+  };
+  methods.chain = Async.chain;
+
+  // ((1 + 1 + 1) * (-1) + 1) * 2 + 1 = -3
+  methods.chain(methods.save, methods.addX, methods.addX, methods.neg,
+                methods.addX, methods.double, methods.addX, methods.save)(1);
+  do_check_eq(methods.x, -3);
+}