I am trying to create new navigation tab in tab--container but having no output. please correct me?

I tried to add a content navigation menu using smarty(Foo Tab) but i am not able to see it happening. What am i doing wrong? because i have also double check the code but no luck. please help me out? 
I am using vagrant machine along with shopware. please let me know any possible solution if there’s any. Thanks

This is code** :**

{extends file="parent:frontend/detail/tabs.tpl"}

{block name="frontend_detail_tabs_navigation_inner"}

    {block name="frontend_detail_tabs_foo"}

{block name="frontend_detail_tabs_content_inner"}

            Foo preview
            Foo Content


This is output after uploading to m server. I expect that there would be a Foo tab along with description tab but no luck.

see https://developers.shopware.com/developers-guide/