It may have been addressed before, but couldn’t find anything with the search.
But why not make your own registration/access? Instead of relying on Google+/Facebook? Or even much better yet, why not use STEAM’s login?
I sign up for betas on Steam all the time, and betas in steam actually force bug reports. Very much unlike what I imagine is what the majority of the people “testing” your game are doing.
Anyways, I signed up with a throwaway Google account to type this out.