Ethereum testnet - arealive/Viper GitHub Wiki
During development, you should run nodes in testnet mode, so that you can test everything out without risking real money. Testnet mode (also known as Morden in Ethereum) is basically identical to the real Ethereum, but the Ether token there has no monetary value. Don’t be lazy and remember to always develop in testnet mode, you will regret it if you lose real Ether due to a programming error.1
[1] https://blog.zeppelin.solutions/the-hitchhikers-guide-to-smart-contracts-in-ethereum-848f08001f05