After lots of research I can say Pre-Registration is open for beta testing.
Use Pre-Registration to Build an Instant User Base
Before you get started with actual beta testing, make sure you consider doing a pre-registration campaign. People who sign up will get a notification when your app launches.
Imagine having a potential installation base of thousands (or maybe even millions) of people, even before your app launches! Here is more information on how pre-registration works…
To setup a pre-registration campaign, contact a Google Business Development manager to get things started. You can use your favorite user acquisition method like paid ads, social media or your email list to drive people to your pre-registration page.
Once you have that setup, it’s time to get back to testing…
Check this link for more information.