How can I know which testnet am I on?
I just ran
bitcoind -testnet, and I would assume it would connect to the most recent one, but is there a way to know it?
To double check, the genesis block for testnet3 (the current version as of this writing) has hash
000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943. So with the daemon running, you can do
bitcoind -testnet getblock 000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943
If you are really on testnet3, you should see "height: 0" in the output.