Ah very nice, they were hinting about adding this.

Was previously using https://cc.dcsec.uni-hannover.de/

I asked about something like this on the sec.SX[1] and at the time it was vaporware. I am glad to see that it is now available. This is a lot better than "openssl s_server"

[1] http://security.stackexchange.com/q/38084/4564