--- a/mail/test/mozmill/folder-display/test-display-message-with-folder-modes.js
+++ b/mail/test/mozmill/folder-display/test-display-message-with-folder-modes.js
@@ -46,29 +46,34 @@
  */
 
 var MODULE_NAME = "test-display-message-with-folder-modes";
 
 var RELATIVE_ROOT = "../shared-modules";
 var MODULE_REQUIRES = ["folder-display-helpers"];
 
 var folder;
+var dummyFolder;
 var smartInboxFolder;
 
 var msgHdr;
 
 function setupModule(module) {
   let fdh = collector.getModule("folder-display-helpers");
   fdh.installInto(module);
 
   // This is a subfolder of the inbox so that
   // test_display_message_in_smart_folder_mode_works is able to test that we
   // don't attempt to expand any inboxes.
   inboxFolder.createSubfolder("DisplayMessageWithFolderModesA", null);
   folder = inboxFolder.getChildNamed("DisplayMessageWithFolderModesA");
+  // This second folder is meant to act as a dummy folder to switch to when we
+  // want to not be in folder.
+  inboxFolder.createSubfolder("DisplayMessageWithFolderModesB", null);
+  dummyFolder = inboxFolder.getChildNamed("DisplayMessageWithFolderModesB");
   make_new_sets_in_folder(folder, [{count: 5}]);
   // The message itself doesn't really matter, as long as there's at least one
   // in the inbox.
   make_new_sets_in_folder(inboxFolder, [{count: 1}]);
 }
 
 /**
  * Test that displaying a message causes a switch to the default folder mode if
@@ -95,39 +100,52 @@ function test_display_message_with_folde
 }
 
 /**
  * Test that displaying a message _does not_ cause a switch to the default
  * folder mode if the folder is present in the current folder mode.
  */
 function test_display_message_with_folder_present_in_current_folder_mode() {
   // Mark the folder as a favorite
-  folder.flags |= Components.interfaces.nsMsgFolderFlags.Favorite;
+  folder.flags |= Ci.nsMsgFolderFlags.Favorite;
+  // Also mark the dummy folder as a favorite, in preparation for
+  // test_display_message_in_smart_folder_mode_works
+  dummyFolder.flags |= Ci.nsMsgFolderFlags.Favorite;
 
   // Make sure the folder doesn't appear in the favorite folder mode just
   // because it was selected last before switching
   be_in_folder(inboxFolder);
 
-  // Switch to favorite folders. Check that the folder is now in the view
+  // Switch to favorite folders. Check that the folder is now in the view, as is
+  // the dummy folder
   mc.folderTreeView.mode = "favorite";
   assert_folder_visible(folder);
+  assert_folder_visible(dummyFolder);
 
   // Try displaying a message
   display_message_in_folder_tab(msgHdr);
 
   assert_folder_mode("favorite");
   assert_folder_selected_and_displayed(folder);
   assert_selected_and_displayed(msgHdr);
 }
 
 /**
  * Test that displaying a message in smart folders mode causes the parent in the
  * view to expand.
  */
 function test_display_message_in_smart_folder_mode_works() {
+  // Clear the message selection, otherwise msgHdr will still be displayed and
+  // display_message_in_folder_tab(msgHdr) will be a no-op.
+  select_none();
+  // Switch to the dummy folder, otherwise msgHdr will be in the view and the
+  // display message in folder tab logic will simply select the message without
+  // bothering to expand any folders.
+  be_in_folder(dummyFolder);
+
   mc.folderTreeView.mode = "smart";
 
   let rootFolder = folder.server.rootFolder;
   // Check that the folder is actually the child of the account root
   assert_folder_child_in_view(folder, rootFolder);
 
   // Collapse everything
   smartInboxFolder = get_smart_folder_named("Inbox");

--- a/mailnews/test/resources/messageInjection.js
+++ b/mailnews/test/resources/messageInjection.js
@@ -110,17 +110,18 @@ function configure_message_injection(aIn
     identity.email = "sender@nul.nul";
     localAccount.addIdentity(identity);
     localAccount.defaultIdentity = identity;
 
     mis.incomingServer = acctMgr.localFoldersServer;
     // Note: Inbox is not created automatically when there is no deferred server,
     // so we need to create it.
     mis.rootFolder = mis.incomingServer.rootMsgFolder;
-    mis.inboxFolder = mis.rootFolder.addSubfolder("Inbox");
+    mis.rootFolder.createSubfolder("Inbox", null);
+    mis.inboxFolder = mis.rootFolder.getChildNamed("Inbox");
     // a local inbox should have a Mail flag!
     mis.inboxFolder.setFlag(Ci.nsMsgFolderFlags.Mail);
     mis.inboxFolder.setFlag(Ci.nsMsgFolderFlags.Inbox);
     _messageInjectionSetup.notifyListeners("onRealFolderCreated",
                                            [mis.inboxFolder]);
 
     // Force an initialization of the Inbox folder database.
     let unused = mis.inboxFolder.prettiestName;