--- a/modules/libjar/zipwriter/test/unit/head_zipwriter.js
+++ b/modules/libjar/zipwriter/test/unit/head_zipwriter.js
@@ -39,18 +39,8 @@ var ZipReader = Components.Constructor("
 
 var tmpDir = do_get_profile();
 var tmpFile = tmpDir.clone();
 tmpFile.append("zipwriter-test.zip");
 if (tmpFile.exists())
   tmpFile.remove(true);
 
 var zipW = new ZipWriter();
-
-do_register_cleanup(function tail_zipwriter() {
-  try {
-    zipW.close();
-  } catch (e) {
-    // Just ignore a failure here and attempt to delete the file anyway.
-  }
-  if (tmpFile.exists())
-    tmpFile.remove(true);
-});

new file mode 100644
--- /dev/null
+++ b/modules/libjar/zipwriter/test/unit/tail_zipwriter.js
@@ -0,0 +1,14 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+try {
+  zipW.close();
+}
+catch (e) {
+  // Just ignore a failure here and attempt to delete the file anyway.
+}
+
+if (tmpFile.exists())
+  tmpFile.remove(true);

--- a/modules/libjar/zipwriter/test/unit/xpcshell.ini
+++ b/modules/libjar/zipwriter/test/unit/xpcshell.ini
@@ -1,10 +1,11 @@
 [DEFAULT]
 head = head_zipwriter.js
+tail = tail_zipwriter.js
 skip-if = toolkit == 'gonk'
 support-files =
   data/test_bug446708/thumbs/st14-1.tiff
   data/emptyfile.txt
   data/smallfile.txt
   data/test.png
   data/test.txt
   data/test.zip

--- a/toolkit/components/contentprefs/tests/unit/head_contentPrefs.js
+++ b/toolkit/components/contentprefs/tests/unit/head_contentPrefs.js
@@ -159,12 +159,8 @@ function inChildProcess() {
 // problems with the tests. Note that we cannot do this in a child process
 // without crashing (but we don't need it anyhow)
 if (!inChildProcess()) {
   var prefBranch = Cc["@mozilla.org/preferences-service;1"].
                    getService(Ci.nsIPrefBranch);
   prefBranch.setBoolPref("browser.preferences.content.log", true);
 }
 
-do_register_cleanup(function tail_contentPrefs() {
-  ContentPrefTest.deleteDatabase();
-  ContentPrefTest.__dirSvc = null;
-});

new file mode 100644
--- /dev/null
+++ b/toolkit/components/contentprefs/tests/unit/tail_contentPrefs.js
@@ -0,0 +1,6 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+ContentPrefTest.deleteDatabase();
+ContentPrefTest.__dirSvc = null;

--- a/toolkit/components/contentprefs/tests/unit/xpcshell.ini
+++ b/toolkit/components/contentprefs/tests/unit/xpcshell.ini
@@ -1,10 +1,11 @@
 [DEFAULT]
 head = head_contentPrefs.js
+tail = tail_contentPrefs.js
 skip-if = toolkit == 'gonk'
 
 [test_bug248970.js]
 [test_bug503971.js]
 [test_bug679784.js]
 [test_contentPrefs.js]
 [test_contentPrefsCache.js]
 [test_getPrefAsync.js]

--- a/toolkit/components/downloads/test/unit/head_download_manager.js
+++ b/toolkit/components/downloads/test/unit/head_download_manager.js
@@ -226,18 +226,8 @@ function oldDownloadManagerDisabled() {
   try {
     // This method throws an exception if the old Download Manager is disabled.
     Services.downloads.activeDownloadCount;
   } catch (ex) {
     return true;
   }
   return false;
 }
-
-do_register_cleanup(function tail_download_manager() {
-  add_task(function test_common_terminate() {
-    // Stop the HTTP server.  We must do this inside a task in "tail.js" until the
-    // xpcshell testing framework supports asynchronous termination functions.
-    let deferred = Promise.defer();
-    gHttpServer.stop(deferred.resolve);
-    yield deferred.promise;
-  });
-});

new file mode 100644
--- /dev/null
+++ b/toolkit/components/downloads/test/unit/tail_download_manager.js
@@ -0,0 +1,24 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * Provides infrastructure for automated download components tests.
+ */
+
+"use strict";
+
+////////////////////////////////////////////////////////////////////////////////
+//// Termination functions common to all tests
+
+add_task(function test_common_terminate()
+{
+  // Stop the HTTP server.  We must do this inside a task in "tail.js" until the
+  // xpcshell testing framework supports asynchronous termination functions.
+  let deferred = Promise.defer();
+  gHttpServer.stop(deferred.resolve);
+  yield deferred.promise;
+});
+

--- a/toolkit/components/downloads/test/unit/xpcshell.ini
+++ b/toolkit/components/downloads/test/unit/xpcshell.ini
@@ -1,10 +1,11 @@
 [DEFAULT]
 head = head_download_manager.js
+tail = tail_download_manager.js
 firefox-appdir = browser
 skip-if = toolkit == 'android' || toolkit == 'gonk'
 support-files =
   downloads_manifest.js
   test_downloads.manifest
   data/digest.chunk
   data/block_digest.chunk
   data/signed_win.exe

--- a/toolkit/components/url-classifier/tests/unit/head_urlclassifier.js
+++ b/toolkit/components/url-classifier/tests/unit/head_urlclassifier.js
@@ -362,12 +362,8 @@ LFSRgenerator.prototype = {
     val = (val >>> 1) | (bit << 31);
     this._value = val;
 
     return (val >>> (32 - bits));
   },
 };
 
 cleanUp();
-
-do_register_cleanup(function tail_ulrclassifier() {
-  cleanUp();
-});

new file mode 100644
--- /dev/null
+++ b/toolkit/components/url-classifier/tests/unit/tail_urlclassifier.js
@@ -0,0 +1,1 @@
+cleanUp();

--- a/toolkit/components/url-classifier/tests/unit/xpcshell.ini
+++ b/toolkit/components/url-classifier/tests/unit/xpcshell.ini
@@ -1,10 +1,11 @@
 [DEFAULT]
 head = head_urlclassifier.js
+tail = tail_urlclassifier.js
 skip-if = toolkit == 'android' || toolkit == 'gonk'
 support-files =
   data/digest1.chunk
   data/digest2.chunk
 
 [test_addsub.js]
 [test_backoff.js]
 [test_dbservice.js]

--- a/toolkit/devtools/apps/tests/unit/head_apps.js
+++ b/toolkit/devtools/apps/tests/unit/head_apps.js
@@ -124,16 +124,9 @@ function do_get_webappsdir() {
         return this;
       }
       throw Cr.NS_ERROR_NO_INTERFACE;
     }
   };
   Services.dirsvc.QueryInterface(Ci.nsIDirectoryService).registerProvider(provider);
 }
 
-do_register_cleanup(function tail_apps() {
-  if (gClient) {
-    // Close the test remote connection before leaving this test.
-    gClient.close(function tail_apps_close() {
-      run_next_test();
-    });
-  }
-});
+

new file mode 100644
--- /dev/null
+++ b/toolkit/devtools/apps/tests/unit/tail_apps.js
@@ -0,0 +1,6 @@
+if (gClient) {
+  // Close the test remote connection before leaving this test
+  gClient.close(function () {
+    run_next_test();
+  });
+}

--- a/toolkit/devtools/apps/tests/unit/xpcshell.ini
+++ b/toolkit/devtools/apps/tests/unit/xpcshell.ini
@@ -1,9 +1,10 @@
 [DEFAULT]
 head = head_apps.js
+tail = tail_apps.js
 skip-if = toolkit == 'android'
 support-files =
   data/app.zip
   data/app-engineering.zip
 
 [test_webappsActor.js]
 skip-if = buildapp == "b2g"

--- a/toolkit/identity/tests/unit/head_identity.js
+++ b/toolkit/identity/tests/unit/head_identity.js
@@ -248,16 +248,9 @@ Services.prefs.setBoolPref("identity.fxa
 
 // after execution, restore prefs
 do_register_cleanup(function() {
   log("restoring prefs to their initial values");
   Services.prefs.setBoolPref("toolkit.identity.debug", initialPrefDebugValue);
   Services.prefs.setBoolPref("identity.fxaccounts.enabled", initialPrefFXAValue);
 });
 
-do_register_cleanup(function tail_identity() {
-  // Pre-emptively shut down to clear resources.
-  if (typeof IdentityService !== "undefined") {
-    IdentityService.shutdown();
-  } else if (typeof IDService !== "undefined") {
-    IDService.shutdown();
-  }
-});
+

new file mode 100644
--- /dev/null
+++ b/toolkit/identity/tests/unit/tail_identity.js
@@ -0,0 +1,8 @@
+
+// pre-emptively shut down to clear resources
+if (typeof IdentityService !== "undefined") {
+  IdentityService.shutdown();
+} else if (typeof IDService !== "undefined") {
+  IDService.shutdown();
+}
+

--- a/toolkit/identity/tests/unit/xpcshell.ini
+++ b/toolkit/identity/tests/unit/xpcshell.ini
@@ -1,10 +1,11 @@
 [DEFAULT]
 head = head_identity.js
+tail = tail_identity.js
 skip-if = toolkit == 'gonk'
 support-files =
   data/idp_1/.well-known/browserid
   data/idp_invalid_1/.well-known/browserid
 
 # Test load modules first so syntax failures are caught early.
 [test_load_modules.js]
 [test_minimalidentity.js]

--- a/uriloader/exthandler/tests/unit/head_handlerService.js
+++ b/uriloader/exthandler/tests/unit/head_handlerService.js
@@ -156,12 +156,8 @@ var HandlerServiceTest = {
     message = "*** HandlerServiceTest: " + message;
     this._consoleSvc.logStringMessage(message);
     print(message);
   }
 
 };
 
 HandlerServiceTest.init();
-
-do_register_cleanup(function tail_handleService() {
-  HandlerServiceTest.destroy();
-});

new file mode 100644
--- /dev/null
+++ b/uriloader/exthandler/tests/unit/tail_handlerService.js
@@ -0,0 +1,5 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+HandlerServiceTest.destroy();

--- a/uriloader/exthandler/tests/unit/xpcshell.ini
+++ b/uriloader/exthandler/tests/unit/xpcshell.ini
@@ -1,10 +1,11 @@
 [DEFAULT]
 head = head_handlerService.js
+tail = tail_handlerService.js
 skip-if = toolkit == 'gonk'
 run-sequentially = Bug 912235 - Intermittent failures
 
 [test_getTypeFromExtension_ext_to_type_mapping.js]
 [test_getTypeFromExtension_with_empty_Content_Type.js]
 [test_handlerService.js]
 support-files = mailcap
 # Bug 676997: test consistently fails on Android