make "rake unittest_backend" not ask for password if it is "storktest"

rake unittest_backend asks for your Postgres password several times even though it is storktest. So I have to run rake unittest_backend PGPASSWORD=storktest. Developer's Guide seems to allude to the fact that this should not be necessary:

Similarly, if the database setup requires a password other than the default storktest, the PGPASSWORD variable can be used by issuing the following command:

$ rake unittest_backend PGPASSWORD=secret123