DOC: ./pam_authentication.sh asks for password

The documentation seems to be not precise enough at the following point:

If you want, you can run a test now: ./pam_authentication.sh asdf ghjk
should print [FAILED] and return with a non-zero exit code.  Unless there is
a user asdf with password ghjk on your system, of course.

In my case, issuing the above command leads to: Enter the password:

in the first place...