--- a/mail/test/mozmill/cloudfile/test-cloudfile-backend-dropbox.js
+++ b/mail/test/mozmill/cloudfile/test-cloudfile-backend-dropbox.js
@@ -185,8 +185,30 @@ function test_deleting_uploads() {
   provider.deleteFile(file, deleteObserver);
   mc.waitFor(function() deleteObserver.success);
 
   // Check to make sure the file was deleted on the server
   assert_equals(1, obs.numSightings(kDeleteFile));
   assert_equals(obs.data[kDeleteFile][0], kFilename);
   Services.obs.removeObserver(obs, kDeleteFile);
 }
+
+/**
+ * Test that when we call createExistingAccount, onStopRequest is successfully
+ * called, and we pass the correct parameters.
+ */
+function test_create_existing_account() {
+  let provider = gServer.getPreparedBackend("someNewAccount");
+  let done = false;
+  let myObs = {
+    onStartRequest: function(aRequest, aContext) {
+    },
+    onStopRequest: function(aRequest, aContext, aStatusCode) {
+      assert_true(aContext instanceof Ci.nsIMsgCloudFileProvider);
+      assert_equals(aStatusCode, Components.results.NS_OK);
+      done = true;
+    },
+  }
+
+  provider.createExistingAccount(myObs);
+  mc.waitFor(function() done);
+}
+

--- a/mail/test/mozmill/cloudfile/test-cloudfile-backend-yousendit.js
+++ b/mail/test/mozmill/cloudfile/test-cloudfile-backend-yousendit.js
@@ -11,17 +11,18 @@ let Cc = Components.classes;
 let Ci = Components.interfaces;
 
 const MODULE_NAME = 'test-cloudfile-backend-yousendit';
 
 const RELATIVE_ROOT = '../shared-modules';
 const MODULE_REQUIRES = ['folder-display-helpers',
                          'compose-helpers',
                          'cloudfile-yousendit-helpers',
-                         'observer-helpers',];
+                         'observer-helpers',
+                         'prompt-helpers',];
 
 Cu.import('resource://gre/modules/Services.jsm');
 
 var gServer, gObsManager;
 
 function setupModule(module) {
   let fdh = collector.getModule('folder-display-helpers');
   fdh.installInto(module);
@@ -36,16 +37,19 @@ function setupModule(module) {
   cbh.installInto(module);
 
   let cyh = collector.getModule('cloudfile-yousendit-helpers');
   cyh.installInto(module);
 
   let oh = collector.getModule('observer-helpers');
   oh.installInto(module);
 
+  let ph = collector.getModule('prompt-helpers');
+  ph.installInto(module);
+
   gObsManager = new cbh.SimpleRequestObserverManager();
 
   // Enable logging for this group of tests.
   Services.prefs.setCharPref("YouSendIt.logging.dump", "All");
 };
 
 function teardownModule(module) {
   Services.prefs.clearUserPref("YouSendIt.logging.dump");
@@ -178,16 +182,39 @@ function test_deleting_uploads() {
   mc.waitFor(function() deleteObserver.success);
 
   // Check to make sure the file was deleted on the server
   assert_equals(1, obs.numSightings(kDeleteFile));
   assert_equals(obs.data[kDeleteFile][0], kFilename);
   Services.obs.removeObserver(obs, kDeleteFile);
 }
 
+/**
+ * Test that when we call createExistingAccount, onStopRequest is successfully
+ * called, and we pass the correct parameters.
+ */
+function test_create_existing_account() {
+  // We have to mock out the auth prompter, or else we'll lock up.
+  gMockAuthPromptReg.register();
+  let provider = gServer.getPreparedBackend("someNewAccount");
+  let done = false;
+  let myObs = {
+    onStartRequest: function(aRequest, aContext) {
+    },
+    onStopRequest: function(aRequest, aContext, aStatusCode) {
+      assert_true(aContext instanceof Ci.nsIMsgCloudFileProvider);
+      assert_equals(aStatusCode, Components.results.NS_OK);
+      done = true;
+    },
+  }
+
+  provider.createExistingAccount(myObs);
+  mc.waitFor(function() done);
+  gMockAuthPromptReg.unregister();
+}
 
 function test_delete_refreshes_stale_token() {
   const kFilename = "testFile1";
   const kUserEmail = "test@example.com";
 
   // Stop the default YSI mock server, and create our own.
   gServer.stop(mc);
   gServer = new MockYouSendItServer();

--- a/mail/test/mozmill/shared-modules/test-prompt-helpers.js
+++ b/mail/test/mozmill/shared-modules/test-prompt-helpers.js
@@ -41,31 +41,74 @@ var Cu = Components.utils;
 
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 
 const MODULE_NAME = 'prompt-helpers';
 
 const RELATIVE_ROOT = '../shared-modules';
 
 // we need this for the main controller
-const MODULE_REQUIRES = [];
+const MODULE_REQUIRES = ['mock-object-helpers'];
 const kMockPromptServiceName = "Mock Prompt Service";
 const kPromptServiceContractID = "@mozilla.org/embedcomp/prompt-service;1";
 const kPromptServiceName = "Prompt Service";
 
+let gMockAuthPromptReg;
+
 function setupModule() {
+  let moh = collector.getModule('mock-object-helpers');
+  gMockAuthPromptReg = new moh.MockObjectReplacer("@mozilla.org/prompter;1",
+                                                  MockAuthPromptFactoryConstructor);
 }
 
 function installInto(module) {
   setupModule();
 
   // Now copy helper functions
   module.gMockPromptService = gMockPromptService;
+  module.gMockAuthPromptReg = gMockAuthPromptReg;
+  module.gMockAuthPrompt = gMockAuthPrompt;
 }
 
+function MockAuthPromptFactoryConstructor() {
+  return gMockAuthPromptFactory;
+}
+
+var gMockAuthPromptFactory = {
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIPromptFactory]),
+  getPrompt: function(aParent, aIID, aResult) {
+    return gMockAuthPrompt.QueryInterface(aIID);
+  }
+}
+
+
+var gMockAuthPrompt = {
+  password: "",
+
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIAuthPrompt]),
+
+  prompt: function MAP_prompt(aTitle, aText, aRealm, aSave,
+                              aDefaultText) {
+    throw Cr.NS_ERROR_NOT_IMPLEMENTED;
+  },
+
+  promptUsernameAndPassword: function
+      MAP_promptUsernameAndPassword(aTitle, aText, aRealm, aSave,
+                                    aUser, aPwd) {
+    throw Cr.NS_ERROR_NOT_IMPLEMENTED;
+  },
+
+  promptPassword: function MAP_promptPassword(aTitle, aText,
+                                              aRealm, aSave,
+                                              aPwd) {
+    aPwd.value = this.password;
+    return true;
+  }
+};
+
 var gMockPromptService = {
   _registered: false,
   QueryInterface: XPCOMUtils.generateQI([Ci.nsIPromptService]),
   _will_return: null,
   _inout_value: null,
   _promptState: null,
   _origFactory: null,
   _promptCb: null,