diff -r 000000000000 -r 6474c204b198 b2g/components/test/mochitest/systemapp_helper.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/b2g/components/test/mochitest/systemapp_helper.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,141 @@
+const Cu = Components.utils;
+
+const { Services } = Cu.import("resource://gre/modules/Services.jsm");
+
+// Load a duplicated copy of the jsm to prevent messing with the currently running one
+let scope = {};
+Services.scriptloader.loadSubScript("resource://gre/modules/SystemAppProxy.jsm", scope);
+const { SystemAppProxy } = scope;
+
+let frame;
+
+let index = -1;
+function next() {
+  index++;
+  if (index >= steps.length) {
+    assert.ok(false, "Shouldn't get here!");
+    return;
+  }
+  try {
+    steps[index]();
+  } catch(ex) {
+    assert.ok(false, "Caught exception: " + ex);
+  }
+}
+
+// Listen for events received by the system app document
+// to ensure that we receive all of them, in an expected order and time
+let isLoaded = false;
+let n = 0;
+function listener(event) {
+  if (!isLoaded) {
+    assert.ok(false, "Received event before the iframe is ready");
+    return;
+  }
+  n++;
+  if (n == 1) {
+    assert.equal(event.type, "mozChromeEvent");
+    assert.equal(event.detail.name, "first");
+  } else if (n == 2) {
+    assert.equal(event.type, "custom");
+    assert.equal(event.detail.name, "second");
+
+    next(); // call checkEventDispatching
+  } else if (n == 3) {
+    assert.equal(event.type, "custom");
+    assert.equal(event.detail.name, "third");
+  } else if (n == 4) {
+    assert.equal(event.type, "mozChromeEvent");
+    assert.equal(event.detail.name, "fourth");
+
+    next(); // call checkEventListening();
+  } else {
+    assert.ok(false, "Unexpected event of type " + event.type);
+  }
+}
+
+
+let steps = [
+  function waitForWebapps() {
+    // We are using webapps API later in this test and we need to ensure
+    // it is fully initialized before trying to use it
+    let { DOMApplicationRegistry } =  Cu.import('resource://gre/modules/Webapps.jsm', {});
+    DOMApplicationRegistry.registryReady.then(function () {
+      next();
+    });
+  },
+
+  function earlyEvents() {
+    // Immediately try to send events
+    SystemAppProxy.dispatchEvent({ name: "first" });
+    SystemAppProxy._sendCustomEvent("custom", { name: "second" });
+    next();
+  },
+
+  function createFrame() {
+    // Create a fake system app frame
+    let win = Services.wm.getMostRecentWindow("navigator:browser");
+    let doc = win.document;
+    frame = doc.createElement("iframe");
+    doc.documentElement.appendChild(frame);
+
+    // Ensure that events are correctly sent to the frame.
+    // `listener` is going to call next()
+    frame.contentWindow.addEventListener("mozChromeEvent", listener);
+    frame.contentWindow.addEventListener("custom", listener);
+
+    // Ensure that listener being registered before the system app is ready
+    // are correctly removed from the pending list
+    function removedListener() {
+      assert(false, "Listener isn't correctly removed from the pending list");
+    }
+    SystemAppProxy.addEventListener("mozChromeEvent", removedListener);
+    SystemAppProxy.removeEventListener("mozChromeEvent", removedListener);
+
+    // Register it to the JSM
+    SystemAppProxy.registerFrame(frame);
+    assert.ok(true, "Frame created and registered");
+
+    frame.contentWindow.addEventListener("load", function onload() {
+      frame.contentWindow.removeEventListener("load", onload);
+      assert.ok(true, "Frame document loaded");
+
+      // Declare that the iframe is now loaded.
+      // That should dispatch early events
+      isLoaded = true;
+      SystemAppProxy.setIsReady();
+      assert.ok(true, "Frame declared as loaded");
+
+      // Once pending events are received,
+      // we will run checkEventDispatching from `listener` function
+    });
+
+    frame.setAttribute("src", "data:text/html,system app");
+  },
+
+  function checkEventDispatching() {
+    // Send events after the iframe is ready,
+    // they should be dispatched right away
+    SystemAppProxy._sendCustomEvent("custom", { name: "third" });
+    SystemAppProxy.dispatchEvent({ name: "fourth" });
+    // Once this 4th event is received, we will run checkEventListening
+  },
+
+  function checkEventListening() {
+    SystemAppProxy.addEventListener("mozContentEvent", function onContentEvent(event) {
+      assert.equal(event.detail.name, "first-content", "received a system app event");
+      SystemAppProxy.removeEventListener("mozContentEvent", onContentEvent);
+
+      next();
+    });
+    let win = frame.contentWindow;
+    win.dispatchEvent(new win.CustomEvent("mozContentEvent", { detail: {name: "first-content"} }));
+  },
+
+  function endOfTest() {
+    frame.remove();
+    sendAsyncMessage("finish");
+  }
+];
+
+next();