public function stop( $args, $assoc_args ) {
		$selenium = $this->_get_executable();
		$pids = trim( shell_exec( "pgrep -l -f {$selenium}" ) );
		$pids = explode( PHP_EOL, (string) $pids );

		if ( ! empty( $pids ) && count( $pids ) >= 1 ) {
			foreach ( $pids as $pid ) {
				shell_exec( "kill -15 {$pid} > /dev/null 2>/dev/null" );
			}
			\WP_CLI::success( 'Selenium server is stopped.' );
		} else {
			\WP_CLI::warning( 'Selenium server is not started yet.' );
		}
	}