Comment by JoshTriplett

While this is an interesting exploration of the history of the Internet, gTLDs, HSTS, and various other things, the story boils down to this: never make up an unregistered domain/TLD and assume it won't exist in the future; always use a reserved test domain/TLD from RFC 2606 (https://tools.ietf.org/html/rfc2606) or the updated RFC 6761 (https://tools.ietf.org/html/rfc6761): .test, .invalid, .example, or .localhost, depending on what semantics you need.