Having the credentials in the environment has the drawback of making them "easily" available to other processes of that user

I set all test environment config in a dedicated test-xterm (with screen inside, so it can proliferate). Something like:

export FOO=foo
export BAR=bar
export PATH=whatever/bin:$HOME/bleadperl/bin:$PATH
export PGPASSFILE=$HOME/.someplace/.pfile
xterm -wf -geometry 200x50 +sb -u8 -fg white -bg black -e "screen -Um 
+-t '${screen_title}'" &
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for instance test database passwords (low value) would be in a file pointed at by one of the env vars (Postgres uses PGPASSFILE).