At the moment if I need to test on mutter (gnome) or kwin (kde) I end up logging out to change window managers.
Ideally I would like to run multiple ones up at the same time. Perhaps it is possible with multiple users logged in at the same time + using waypipe?
It is useful that I have a specific failure (in eclipse-platform/eclipse.platform.swt#2826 (comment)) to see if I have reproduced the problems adequately.