Comment 4 for bug 1271054

This is what the notes-app tests do at startup:

    def setUp(self):
        self.pointing_device = Pointer(self.input_device_class.create())
        super(NotesAppTestCase, self).setUp()
        self.launch_app()
        self.main_window.visible.wait_for(True)
        self.main_window.close_toolbar()

Could it be that (main_window.visible == True) is still too early to start interacting with the application, and we could use a more reliable assertion to verify that the application is ready to be interacted with?