There is a great option to run SWTBot tests in separate window. No more watching SWTBot "doing the work"

This can be accomplished by Xephyr. As a Xorg extension it should be available on every linux distro.

Xephyr is  able to run another X session in a window in current session. The only problem is, that you cannot run multiple (gnome/xfce/kde) sessions at one time. I recommend to install some lightweight desktop manager like fluxbox, twm, enlightenement etc or run nested session under different user.

I've created simple shell script called nestedX which can do some bothering stuff for you. Just pick it, slightly edit (comment out you favorite wm) and use.

Once nestedX runs, new session in window  should appear.
Eclipse with SWTBot tests and of course whatever can run inside.
When developing tests and you've started your IDE in current session, you can modify run configuration of your SWTBot test and define environment variable DISPLAY with value of new display (nestedX script tells it).

There is also an option to pass a program as an argument to script. Program will be executed few seconds after starting window manager in nested session.