MockMyID is a Mozilla Persona Identity Provider (IdP) that will gladly issue assertions to anyone and everyone, without a second thought.
It's like Mailinator, for Persona.
(All email sent to mockmyid.com addresses is delivered and readable at Mailinator!)
MockMyID makes it easy to test and demo sites that use Persona.
Whenever you're asked to log in with Persona, just make up any email address you want @mockmyid.com.