SwingTest in the jkernel tries to use some of internal deployment components including progress.

After recent refactoring (7009157) default animation panel is initialized if appletviewer is created.
However, SwingtTest creates appletviewer and attempts to use it without properly initializing environment.
AppletViewer is not ready that browser services are not available and fails trying to cast.

Note that SwingTest also has the problem as it may not simulate deployment behavior as close as one may want.
But this is separate issue to be adressed in the jkernel if needed.