Cardano staging environment for a quick Proof of Concept

Hello everybody.

I’m building a proof of concept to accept ADA as payment.
Essentially, my script creates wallet for the clients to send ADA into, so when I see new balance in those wallets,
I know a payment has been made.

What I want to do is to validate the concept by creating some acceptance (BDD style) tests, and in order to do that
I’m spawning a docker container running a node connected to the testnet, that I can use as the api interfacing with Cardano.
So far, I’ve been able to do that, but now I’m wondering how can I get some ADA into one of the wallets to test the balance detection.

I’ve read about the testnet faucet but I cannot find if it can be called via API, and if
there’s a way to get the ADA almost instantly, since these would be automated tests and I need them to run as fast as possible.

Also, reading through the faucet page, I see that returning the ADA after the tests is required, so that makes me wonder if I’m using
the correct approach, or should I try to create a private Cardano blockchain where I can assign ADA in the genesis block.

Any tips or guidance that you can provide? Thank you very much in advance!