Android In-App billing testing with another account

I'm trying to test In-App billing subscriptions. My personal account and my developer account are the same. I can't buy my own products with my account, so, I need to test with another account (if a Google guy reads that: it SUCKS!!!!! Please change this, it is such a pain for us!). Here are the steps I followed:

• created a new account (lets call it account B)
• added account B on Google Play on my phone
• uploaded a signed apk for beta test
• created a beta testers list and added account B
• connected to account B on my phone in Firefox, went to the test link, opted-in, and installed the app (from Firefox, not from Play Store)
• bought an item
• been charged (and auto-refunded myself -_- ...)

So, seems like its not exactly working. After reading again the developer guides, I saw that when an account is set as a tester account, it is clearly stated in the in-app billing popup that you will not been charged. There is nothing in my popups.

Does anyone know where can be the mistake?

I saw on some questions on stackoverflow that it might not be possible to have a phone set up for testing if the testing account is not the primary account on Google Play app, is that true?