The Ethereum Go client (https://geth.ethereum.org) Geth, can be connected to the test network using the following command:
$ geth --testnet
A sample output is shown in the following screenshot. The screenshot shows the type of the network chosen and various other pieces of information regarding the blockchain download:
The output of the geth command connecting to Ethereum test net
A blockchain explorer for testnet is located at https://ropsten.etherscan.io can be used to trace transactions and blocks on the Ethereum test network.
There are other test networks available too, such as Frontier, Morden, Ropsten, and Rinkeby. Geth can be issued with a command-line flag to connect to the desired network:
--testnet: Ropsten network: pre-configured proof-of-work test network --rinkeby: Rinkeby network: pre-configured proof-of-authority test network --networkid value:...
