Electrum-3.3.8 or up
Start Electrum on testnet and create a default wallet:
./Electrum --testnet
Configure and start Electrum as a daemon :
./Electrum --testnet setconfig rpcuser user
./Electrum --testnet setconfig rpcpassword pass
./Electrum --testnet setconfig rpcport 7777
./Electrum --testnet daemon
./Electrum --testnet daemon load_wallet