Twitter Card application process for sites prior to launch


Hi there - apologies for the newbie question. We are currently finishing development of our site and getting ready to launch.
We’d like to launch with Twitter photo cards implemented.

We’ve tested twitter photo card using the preview tool but the actual site * is still just a basic landing page as the site is not yet publicly accessible. Will this impact the application process or cause the application to be rejected?
I couldn’t find any discussion on how developers test and get approval pre-product launch.

Thanks in advance.