In App Purchase Testing ,When you use Google Play In-app Billing to sell items, Google Play handles the checkout details so your app never has to process financial transactions. Your app will use the same checkout flow which is used for content purchases on Google Play, so users will get a familiar, reliable, and secure experience.

The Google Play Billing Library simplifies the development process for billing, allowing you to focus your efforts on implementing logic specific to your app. It provides a straightforward and simple interface for sending in-app billing requests and managing in-app billing transactions, and saves you integration time when new features are launched.