You don't even need testnet in a box anymore. Bitcoin Core comes with a regression test mode which allows you to set up your own private test network independent of everyone else.
I have tried out testnet when creating paper wallets, and i must say testnet itself is not really usable (in my experience and opinion, i don't want to start a big discussion about this).... I sent coins to a testnet address on a testnet paper wallet, but a testnet android client couldn't sweep the paper wallet.
In the end, i installed bitcoin core, started it in testnet mode and imported the private keys on the paper wallet to recuperate the (worthless) testnet coins.
I think knightdk might have given you the best sollution in case you're just trying out stuff locally. If you're in need of a real network, you might try out an altcoin??? Download a new, cpu or gpu minable altcoin, solo mine a couple of blocks, and use it to test out your programming
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