During the closed beta testing, I have spent quite a lot of time getting the in-app product to work properly in my game. The coding is quite complex (at first), and it took me almost a week to understand everything. To test the code you need to publish your app in alpha or beta stage within google developer console. Every time I finish fixing the code and upload the new version to the google play store server, it took me several hours to download the new version into my testing device. It is understandable since the server serve millions of apps and it take some time for the server to readily distribute the (testing) app. After four revisions, finally I get the in-app product to work flawlessly. I also have test it my self by (fake) purchasing the ‘remove ads’ in-app product. You will get a notification during this testing stage that your ‘digital purchase’ will not be charged by Google Play Store.