public function start( $args, $assoc_args ) {
		$selenium = $this->_get_executable();
		if ( is_executable( $selenium ) ) {

			$pids = explode( PHP_EOL, trim( shell_exec( "pgrep -f {$selenium}" ) ) );
			if ( count( $pids ) < 2 ) {
				shell_exec( "{$selenium} > /dev/null 2>/dev/null &" );
				\WP_CLI::success( 'Selenium server started.' );
			} else {
				\WP_CLI::warning( 'Selenium server is already started.' );
			}

		} else {
			\WP_CLI::error( 'Selenium server is not executable or not installed.' );
		}
	}