No Example for Steam IAP (microtransaction)

Hello, first of all. I wanna say thanks to you for this very useful assets.

I want to make an IAP for my game but i can't find any example for Steam IAP. I found microTransaction on SteamUserTest.cs but the callback isn't responding. I was new on publishing in steam so...

Can you upload an example project or script that using Steam IAP, please? :))
Thanks!