There is an alternate blockchain explicitly created for testing called the "testnet." It works exactly like Bitcoin except its genesis block is different, so it

There is an alternate blockchain explicitly created for testing called the "testnet." It works exactly like Bitcoin except its genesis block is different, so it has a different blockchain and set of transactions. Testcoins have no value, and the mainstream client switches to a new testchain every so often. Lose testcoins, not Bitcoins.