void enableFilter(SimulatedArchivalUnit sau, boolean enable)
     throws ArchivalUnit.ConfigurationException {
   Configuration auConfig = sau.getConfiguration().copy();
   // no bad file when playing with filtering
   auConfig.remove("badCachedFileLoc");
   auConfig.remove("badCachedFileNum");
   if (enable) {
     auConfig.put(SimulatedPlugin.AU_PARAM_HASH_FILTER_SPEC, "true");
   } else {
     auConfig.remove(SimulatedPlugin.AU_PARAM_HASH_FILTER_SPEC);
   }
   sau.setConfiguration(auConfig);
 }