I'd like to add an API_KEY for GoogleMaps for testing and in documentation I've read this :
Tip: During development and testing, you can register a project for testing purposes in the Google Cloud Platform Console and use a generic, unrestricted API key. When you are ready to move your app into production, register a separate project for production, create an Android-restricted API key, and add the key to your application.
My question is, do I have to put my Credit card even if it's a testing API_KEY? I do not get the purpose to put my Creadit card to use Google Maps, isn't it free?
Updated Answer
As of June11, 2018 it is now mandatory to have a billing account to get API key. You can still make keyless calls to the Maps JavaScript API and Street View Static API which will return low-resolution maps that can be used for development. Enabling billing still gives you $200 free credit monthly for your projects.
This answer is no longer valid
As long as you're using a testing API key it is free to register and use. But when you move your app to commercial level you have to pay for it. When you enable billing, google gives you $200 credit free each month that means if your app's map usage is low you can still use it for free even after the billing enabled, if it exceeds the credit limit now you have to pay for it.