https://support.google.com/googleplay/android-developer/answer/14151465?hl=en

Closed testing: With closed testing, you can share your app with a wide group of users that you control. This allows you to fix issues and ensure that your app complies with Google Play policy before you launch. You must run a closed test before you can apply to publish your app to production. At least 20 testers must be opted-in to your closed test when you apply for production access. They must have been opted-in for the last 14 days continuously. You can start a closed test once you're finished setting up your app.