Warning: call_user_func_array()

<?php
/*
Plugin Name: test system
Plugin URI:
Description:
Author:
Version: 1.0
Author URI:
*/

/* Instantiate new class */
$test_system = new test_system();

/* Visual Form Builder class */
class test_system {

	 function __construct(){
		global $wpdb;

		/* Setup global database table names */
		$this->testing_table_name = $wpdb->prefix . 'test_system_testing';

			/* Add a database version to help with upgrades and run SQL install */
			if ( !get_option( 'test_system_db_version' ) ) {
				update_option( 'test_system_version', $this->test_system_version );
				$this->install_db();
			}

			/* If database version doesn't match, update and run SQL install */
			if ( get_option( 'test_system_db_version' ) != $this->test_system_db_version ) {
				update_option( 'test_system_db_version', $this->test_system_db_version );
				$this->install_db();
			}
	}

	static function install_db() {
		global $wpdb;

		$testing_table_name = $wpdb->prefix . 'test_system_testing';

		/* Explicitly set the character set and collation when creating the tables */
		$charset = ( defined( 'DB_CHARSET' && '' !== DB_CHARSET ) ) ? DB_CHARSET : 'utf8';
		$collate = ( defined( 'DB_COLLATE' && '' !== DB_COLLATE ) ) ? DB_COLLATE : 'utf8_general_ci';

		require_once( ABSPATH . 'wp-admin/includes/upgrade.php' );

		$testing_sql = "CREATE TABLE $testing_table_name (
				testing_id BIGINT(20) NOT NULL AUTO_INCREMENT,
				user_name VARCHAR(255),
				password VARCHAR(255),
				title VARCHAR(255),
				first_name VARCHAR(255),
				surname VARCHAR(255),
				country VARCHAR(255),
				address_line_1 VARCHAR(255),
				address_line_2 VARCHAR(255),
				county VARCHAR(255),
				post_code VARCHAR(8),
				daytime_telephone_number VARCHAR(12),
				evening_telephone_number VARCHAR(12),
				mobile VARCHAR(11),
				email VARCHAR(255),
				UNIQUE KEY  (testing_id)
			) DEFAULT CHARACTER SET $charset COLLATE $collate;";

		/* Create or Update database tables */
		dbDelta( $testing_sql );
	}


}

register_activation_hook( __FILE__, 'test_system','install_db' );

?>