su without password with pam su-authentication

I've done the following configuration in ubuntu 14.04 but it's still asking password.

$ /etc/passwdtest:x:1004:1004::/home/test:/bin/bash$/etc/pam.d/su auth       required   pam_wheel.so group=test auth       sufficient pam_wheel.so trust use_uid

Is there any other method to do this?