An alternative bitcoin blockchain used solely for testing purposes. Testnet is like mainnet , but has a different genesis block. It has been reset several times. The latest testnet is testnet3. Testnet uses slightly different address format to avoid confusion with the main Bitcoin addresses.
Malone, J.A (2015). Glossary of Bitcoin Terms and Definitions. United States: Lulu Press, Inc
A mirror network of the production Ethereum network that is meant for testing. See Morden.