From online documentation, it seems that that there is a pg_regress program/component for regression tests.
REGRESS_OPTS
additional switches to pass to **pg_regress**
I can do simple regression tests (under postgresql coming from Ubuntu 16.04 LTS), but couldn't find the program pg_regress itself or see its options.
$ pg_regress
pg_regress: command not found
which pg_regress returns empty.
Do I need to install additional packages to get pg_regress or is it hidden somewhere?
pg_regress is available from the source code repository. If you installed PostgreSQL through a package manager or as a binary, it will not be included. Regression testing is typically done after you build the code yourself, for instance with a new release.