class ErrorTestController

class ErrorTestController extends ControllerBase {
    
    /**
     * The database connection.
     *
     * @var \Drupal\Core\Database\Connection
     */
    protected $database;
    
    /**
     * Constructs a \Drupal\error_test\Controller\ErrorTestController object.
     *
     * @param \Drupal\Core\Database\Connection $database
     *   The database connection.
     */
    public function __construct(Connection $database) {
        $this->database = $database;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('database'));
    }
    
    /**
     * Generate warnings to test the error handler.
     */
    public function generateWarnings($collect_errors = FALSE) {
        // Tell Drupal error reporter to collect test errors or not.
        define('SIMPLETEST_COLLECT_ERRORS', $collect_errors);
        // This will generate a notice.
        $notice = new \stdClass();
        $notice == 1 ? 1 : 0;
        // This will generate a warning.
        $obj = new \stdClass();
        $obj->p =& $obj;
        var_export($obj, TRUE);
        // This will generate a user error. Use & to check for double escaping.
        trigger_error("Drupal & awesome", E_USER_WARNING);
        return [];
    }
    
    /**
     * Generate fatal errors to test the error handler.
     */
    public function generateFatalErrors() {
        $function = function (array $test) {
        };
        // Use an incorrect parameter type, string, for testing a fatal error.
        $function("test-string");
        return [];
    }
    
    /**
     * Trigger an exception to test the exception handler.
     *
     * @param string $argument
     *   A function argument which will be included in the exception backtrace.
     *
     * @throws \Exception
     */
    public function triggerException(string $argument = "<script>alert('xss')</script>") : void {
        define('SIMPLETEST_COLLECT_ERRORS', FALSE);
        // Add function arguments to the exception backtrace.
        ini_set('zend.exception_ignore_args', FALSE);
        ini_set('zend.exception_string_param_max_len', 1024);
        throw new \Exception("Drupal & awesome");
    }
    
    /**
     * Trigger an exception to test the PDO exception handler.
     */
    public function triggerPDOException() {
        define('SIMPLETEST_COLLECT_ERRORS', FALSE);
        $this->database
            ->select('bananas_are_awesome', 'b')
            ->fields('b')
            ->execute();
    }
    
    /**
     * Trigger an exception during rendering.
     */
    public function triggerRendererException() {
        return [
            '#type' => 'page',
            '#post_render' => [
                function () {
                    throw new \Exception('This is an exception that occurs during rendering');
                },
            ],
        ];
    }

}