Temporary, In-memory Postgres DB?

This is a real longshot, but here goes...

Is there such a thing as a temporary, probably in-memory, version of a
Postgres DB? Sort of like SQLite, only with the features/function of
PG? A DB like this would exist inside of, and for the duration of, a
script/program that created it, then vanish when the script/program
ends.

Probably not, but if not, then this would be (IMO) a great addition to
have, something that'd really make it distinct from MySQL . I'd use
SQLite, but I want to have stored functions and other "real" database
features that it just doesn't have.

Thanks

-dave