/*
  * Assert that a feature with the given id exists in the configuration. If
  * a version is specified then match the version, otherwise any version will
  * do.
  */
 public void assertFeatureExists(
     String message, Configuration configuration, String id, String version) {
   List sites = configuration.getSites();
   assertNotNull(message, sites);
   boolean found = false;
   for (Iterator iter = sites.iterator(); iter.hasNext(); ) {
     Site site = (Site) iter.next();
     Feature[] features = site.getFeatures();
     for (int i = 0; features != null && i < features.length; i++) {
       if (id.equals(features[i].getId())) {
         if (version == null) found = true;
         else if (version.equals(features[i].getVersion())) found = true;
       }
     }
   }
   assertTrue(message, found);
 }