What are Google Test Tracks and how to use those?

Private applications and applications published in Google Play can be tested via Google Play Developer Console’s test tracks before going live

HMD Enable Pro provides an option to take the application test tracks into use via Policy’s application setting.

To access the Developer Console for the private applications added via the Google Play iFrame, “Make advanced edits” selection needs to be chosen from the application details. Google instructions on enabling the test tracks can be found at: Set up an open, closed, or internal test - Play Console Help (google.com). 

Along setting up the test track on the Google Play console, application settings need to be adjusted via a new or existing policy in EMM management console. Upon the deployment, the devices are updated with the test track APK version as per Google Play app update rules to be found at: Manage app updates - Managed Google Play Help.