Logged in as Test User to post to group in app while in development mode, but failed.
According to this bug report https://developers.facebook.com/support/bugs/374244166706163/ It works only when I'm an admin of both the app and group.
To request Groups API permission in App review section, I have to reproduce my application's functionalities using a test user. How am I supposed to do that if my developer account is the only one able to successfully post to group?