static class ErrorInducingInterceptor extends CommandInterceptor {
@Override
public Object visitPutKeyValueCommand(InvocationContext ctx, PutKeyValueCommand command) throws Throwable {
Object k = command.getKey();
if (k == FailureType.EXCEPTION_FROM_INTERCEPTOR)
throw new EmptyStackException();
else if (k == FailureType.ERROR_FROM_INTERCEPTOR)
throw new ClassCircularityError();
else
return super.visitPutKeyValueCommand(ctx, command);
}