Running another instance of bitcoin-qt dedicated to testnet/regtest? Is it possible to run another instance of bitcoin-qt dedicated to testnet/regtest? If so, how do i do this?

My question is similar to "Running two bitcoind instances for different nets," but I want to associate bitcoin-qt, not just bitcoind, with the testnet/regtest.
Depending on your OS you can start a 2nd bitcoin-qt acting on a non-mainnet with ./bitcoin-qt -testnet or ./bitcoin-qt -regtest (from a shell). You can also define a custom datadir and place a bitcoin.conf there (use bitcoin-qt -datadir=&lt;path&gt;).

On OSX/Mac you would need to use Terminal and run something like /Applications/Bitcoin-Qt.app/Contents/MacOS/Bitcoin-Qt -regtest