call_user_func_array() expects parameter 1 to be a valid callback

Hello I have problem with my plugin :/

Warning: call_user_func_array() expects parameter 1 to be a valid callback, function ‘wp_slider_info_page’ not found or invalid function name in C:\xampp\htdocs\wordpress\wp-includes\plugin.php on line 496

I found many topics about this warning but I still don’t know what is wrong.. :/

if ( !class_exists( 'wp_slider' ) ) {

	class wp_slider{

		function __construct() {

			add_action( 'admin_menu', array( $this, 'wp_slider_info' ) );
			add_action( 'slider-style', array( $this, 'slider_styles') );
			add_action( 'slider-script', array( $this, 'slider_scripts') );

			add_filter( 'the_content', array( $this, 'wp_slider_info_page') );

			register_activation_hook( __FILE__, array( $this, 'wp_install' ) );
			register_deactivation_hook(__FILE__, array( $this, 'wp_uninstall' ) );
		}

		function wp_slider_info(){

			add_menu_page('wp Slider', 'wp Slider', 'administrator', 'slider-info', 'wp_slider_info_page', 'dashicons-format-video');
		}

		function wp_install(){
			global $wpdb;
			$table_name=$wpdb->prefix.'wp_slider';
			$sql="CREATE TABLE $table_name (
			id int(11) NOT NULL AUTO_INCREMENT,
			image varchar(255) NOT NULL,
			link varchar(255) NOT NULL,
			title varchar(255) NOT NULL,
			content text NULL,
			UNIQUE KEY id (id)
			);";

			require_once( ABSPATH . 'wp-admin/includes/upgrade.php' );
			dbDelta( $sql );
		}

		function wp_uninstall(){
			global $wpdb;
			$table_name=$wpdb->prefix.'wp_slider';
			$sql='DROP TABLE '.$table_name;
				$wpdb->query($sql);
		}

		public function slider_scripts() {

			if (!is_admin()) {
				wp_register_style('slider-script', plugins_url('slider-script.js', __FILE__), array( 'jquery' ));
				wp_enqueue_style('slider-script');
			}
		}

		public function slider_styles( $page ) {

			wp_register_style('slider-style', plugins_url('slider-style.css', __FILE__));
			wp_enqueue_style('slider-style');
		}

		function wp_slider_info_page( $content ){

			return $content . '<p>Test</p>';
		}

	}

	new wp_slider();

}