Opening GUI as another user

[Dotan Cohen]

In addition to my regular user, I have created another user, "test",
to test things. When I work as this user in Konsole, I cannot open GUI
applications:
dotancohen at ubuntu:~$ su - test
Password:
test at ubuntu:~$ kate
kate: cannot connect to X server
test at ubuntu:~$ gedit
cannot open display: (null)
Run 'gedit --help' to see a full list of available command line options.
test at ubuntu:~$ firefox

(firefox-bin:13339): Gtk-WARNING **: cannot open display:
test at ubuntu:~$

What can I do to have the user "test" open GUI apps from Konsole? Thanks.

Dotan Cohen
http://what-is-what.com