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