diff --git a/testing/mochitest/jetpack-addon-harness.js b/testing/mochitest/jetpack-addon-harness.js
index 6c45289fe707..6f9db61ddf4a 100644
--- a/testing/mochitest/jetpack-addon-harness.js
+++ b/testing/mochitest/jetpack-addon-harness.js
@@ -9,6 +9,7 @@ if (Cc === undefined) {
 
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.import("resource://gre/modules/Task.jsm");
+Cu.import("resource://gre/modules/Timer.jsm");
 
 XPCOMUtils.defineLazyModuleGetter(this, "Services",
   "resource://gre/modules/Services.jsm");
@@ -74,10 +75,18 @@ function installAddon(url) {
           resolve(addon);
         },
 
+        onDownloadCancelled: function(install) {
+          reject("Download cancelled: " + install.error);
+        },
+
         onDownloadFailed: function(install) {
           reject("Download failed: " + install.error);
         },
 
+        onInstallCancelled: function(install) {
+          reject("Install cancelled: " + install.error);
+        },
+
         onInstallFailed: function(install) {
           reject("Install failed: " + install.error);
         }
@@ -96,10 +105,11 @@ function uninstallAddon(oldAddon) {
         if (addon.id != oldAddon.id)
           return;
 
+        dump("TEST-INFO | jetpack-addon-harness.js | Uninstalled test add-on " + addon.id + "\n");
+
         // Some add-ons do async work on uninstall, we must wait for that to
         // complete
-        let timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
-        timer.init(resolve, 500, timer.TYPE_ONE_SHOT);
+        setTimeout(resolve, 500);
       }
     });
 
@@ -119,13 +129,13 @@ function waitForResults() {
 }
 
 // Runs tests for the add-on available at URL.
-let testAddon = Task.async(function*({ url, expected }) {
+let testAddon = Task.async(function*({ url }) {
   dump("TEST-INFO | jetpack-addon-harness.js | Installing test add-on " + realPath(url) + "\n");
   let addon = yield installAddon(url);
 
   let results = yield waitForResults();
 
-  dump("TEST-INFO | jetpack-addon-harness.js | Uninstalling test add-on " + realPath(url) + "\n");
+  dump("TEST-INFO | jetpack-addon-harness.js | Uninstalling test add-on " + addon.id + "\n");
   yield uninstallAddon(addon);
 
   dump("TEST-INFO | jetpack-addon-harness.js | Testing add-on " + realPath(url) + " is complete\n");
@@ -197,6 +207,8 @@ function testInit() {
         }
 
         if (config.closeWhenDone) {
+          dump("TEST-INFO | jetpack-addon-harness.js | Shutting down.\n");
+
           const appStartup = Cc['@mozilla.org/toolkit/app-startup;1'].
                              getService(Ci.nsIAppStartup);
           appStartup.quit(appStartup.eAttemptQuit);
@@ -208,6 +220,7 @@ function testInit() {
           return finish();
 
         let filename = fileNames.shift();
+        dump("TEST-INFO | jetpack-addon-harness.js | Starting test add-on " + realPath(filename.url) + "\n");
         testAddon(filename).then(results => {
           passed += results.passed;
           failed += results.failed;