Testing in-app billing before releasing a new version of an application

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http://stackoverflow.com – I have a free application in which I want to add a premium product. I'm developing the new code while maintaining the older version for bugfixes. Now I would like to test IAB integration at least with my personal phone (not the best idea), but Google Play doesn't allow me to add in-app products until I add the BILLING permission, and in fact the currently release version doesn't. The question comes straightforward: how can I add in-app products before releasing a new version of the application? If I must add the BILLING (and also the RECEIVE_BOOT_COMPLETED) permission before implementing the (HowTos)