diff -r 000000000000 -r 6474c204b198 toolkit/devtools/server/tests/unit/test_nesting-01.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/devtools/server/tests/unit/test_nesting-01.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,48 @@
+/* -*- Mode: javascript; js-indent-level: 2; -*- */
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Test that we can nest event loops when needed in
+// ThreadActor.prototype.synchronize.
+
+var gClient;
+var gThreadActor;
+
+function run_test() {
+  initTestDebuggerServer();
+  let gDebuggee = addTestGlobal("test-nesting");
+  gClient = new DebuggerClient(DebuggerServer.connectPipe());
+  gClient.connect(function () {
+    attachTestTabAndResume(gClient, "test-nesting", function (aResponse, aTabClient, aThreadClient) {
+      // Reach over the protocol connection and get a reference to the thread actor.
+      gThreadActor = aThreadClient._transport._serverConnection.getActor(aThreadClient._actor);
+
+      test_nesting();
+    });
+  });
+  do_test_pending();
+}
+
+function test_nesting() {
+  const thread = gThreadActor;
+  const { resolve, reject, promise: p } = promise.defer();
+
+  let currentStep = 0;
+
+  executeSoon(function () {
+    // Should be on the first step
+    do_check_eq(++currentStep, 1);
+    // We should have one nested event loop from synchronize
+    do_check_eq(thread._nestedEventLoops.size, 1);
+    resolve(true);
+  });
+
+  do_check_eq(thread.synchronize(p), true);
+
+  // Should be on the second step
+  do_check_eq(++currentStep, 2);
+  // There shouldn't be any nested event loops anymore
+  do_check_eq(thread._nestedEventLoops.size, 0);
+
+  finishClient(gClient);
+}