Firebase Plan Payment For Stripe Integration

I am developing a mobile application in Android. I am looking to integrate a payment system in my application and I saw that the trio firebase + android + stripe was the best in my case. I understood that it was necessary to use firebase cloud functions to act as a back-end management server for Stripe (https://github.com/firebase/functions-samples/tree/Node-8/stripe) but it It says "Enable billing on your project by switching to the Blaze or Flame plan." See pricing for more details. But, I use the free version of firebase, can I implement this solution in test mode or I have to change the firebase subscription automatically

You can't integrate with Stripe using Cloud Functions on the free plan, because that plan has a limitation where it's not able to make outgoing connections to endpoints that are not fully controlled by Google. This is set in place in order to prevent abuse. You will have to provide billing information and upgrade to a paid plan.