I don't think that what's friends are for (to test your app). Meaning, you'll need to go to a paying service, making it harder to justify afterwards to make your app free without ads or in-app purchase.
I don't even have 20 friends. But if you/your team have 15 acquaintances who are willing, you can set up five Google accounts to test the app. After all, all you need for a Google account is a phone number. Which, at least in my country, can be acquired for free without much hassle.