Amazon has released a tool that lets you test mobile apps on a group of users before going fully live.
Live App Testing is designed for use with mobile apps in the Amazon Appstore, for any Android or Amazon Fire device, including Fire TV and Fire phone. To use it you create a version of your app, upload it onto the Amazon Developer Portal, then choose Live App Testing. You can then set up a group of testers by adding their email addresses to the group in Live App Testing. When you say you want the test to start, your test group will receive an email with instructions to download the test app and begin testing against Amazon’s production environment. No one other than the test group will be able to download your app.

Link ~> https://developer.amazon.com/public/community/post/TxCVSAM1IG7NX2/Launch-Better-Apps-Announcing-Live-App-Testing