SvgPanelTest is a very simple plasmoid that can be used by theme designers to test Plasma themes, you can load different themes with its configuration interface, as well as disabling the rendering of an edge of the svg.
it can be used in plasma or in plasmoidviewer with the command
or, with a very recent svn snapshot
plasmoidviewer svgpaneltest /path/to/your/theme.svg
To build it a KDE4 developing environment is needed (see http://techbase.kde.org/index.php?title=Getting_Started/Build/KDE4)
at least KDE 4.0.2 is required, but a recent svn snapshot is preferred.