Step by step guide how to implement In-App purchases in Android app using Google play Billing API.
Check the post. which explain how to develop and test the in-app purchase
Steps to test this app,
Download the source code. Change the Packagename. Test the source code in local environment. Sign the APK. Upload APK to google play to Alpha Release. Assign testers. Licence the tester through google play. Let Tester enjoy the app.