Can i run filecoin privately on 3-4 nodes and does it have a testnet?

HI everyone,
I want to make a cluster of private nodes which upload files among themselves
Will that require setting up testnet and spending test filecoins ?

Thanks for the question. You can get started running a private network here: https://github.com/filecoin-project/go-filecoin/wiki/Running-a-network-locally

You can distribute FIL tokens among your nodes in the genesis block.