The problem is that you need a local email server that can receive your emails. To test the setup in development install the mailcatcher gem, that you will use as a SMTP server in development, catching all incoming mails and displaying them on http://localhost:1080/:
Just run in the terminal
gem install mailcatcher
then run mailcatcher
in the console. A toy SMTP server will be running on port 1025 catching emails and displaing them on HTTP port 1080.
Then just goto the spree admin panel and configure it. The following settings work perfectly for me without any code writing.
After I clicked on send test mail
I got the following email on my localhost: