def options(self, parser, env):
        """Register commandline options.
        """
        parser.add_option('--collect-only',
                          action='store_true',
                          dest=self.enableOpt,
                          default=env.get('NOSE_COLLECT_ONLY'),
                          help="Enable collect-only: %s [COLLECT_ONLY]" %
                          (self.help()))