I'm working on Apex Test Class. If anyone knows the problem the below test code. Thanks!

The Class is returning Object sumBalance with SUM values (alias: bl, bt, pt) from SOQL and component receives {v.sumBalance.bl}, {v.sumBalance.bt},  {v.sumBalance.pt}. These are working fine. But can't figure out how to test this Class....

Class

public with sharing class DueBalanceController{
    @AuraEnabled
    public static Object sumBalance (String recordId){
        Date d_today = system.Date.today();
        AggregateResult[] groupedResults = [
            SELECT SUM(Balance__c)bl,SUM(Paid_Total__c)pt,SUM(Billing_Total__c)bt, Tenant__c
            FROM Billing__c 
            WHERE Tenant__c	= :recordId AND User_Due_Date__c <= :d_today AND (Status__c='Unpaid' OR Status__c='Paid' OR Status__c='Captured')
            GROUP BY Tenant__c
        ];
        Object sumAmount = groupedResults[0];
        return sumAmount;
    }
}

Test Class

@isTest
public class DueBalanceControllerTest {
        
    @isTest 
    public static void testDueBalanceController(){
        String recordTypeId  = Schema.getGlobalDescribe().get('Account').getDescribe().getRecordTypeInfosByName().get('Person Account').getRecordTypeId();
        Account acct= new Account(
          RecordTypeID = recordTypeId ,
          FirstName = 'Test FName',
          LastName='Test LName',
          PersonMailingStreet='test@yahoo.com',
          PersonMailingPostalCode='12345',
          PersonMailingCity='SFO',
          PersonEmail='test@yahoo.com',
          PersonHomePhone='1234567',
          PersonMobilePhone='12345678' 
        );
        insert acct;
        
        Case cs = new Case(
        	Subject='Test',
            Status ='Closed'
        );
        insert cs;
            
        Billing__c bl = new Billing__c(Name='Test');
        bl.Monthly_Rent__c = 200000;
        bl.Paid_Total__c = 100000;
        bl.Status__c = 'Paid';
        bl.User_Due_Date__c = system.Date.today()-20;
        bl.Tenant__c = acct.Id;
        bl.Case__c = cs.Id;
        insert bl;
    
    Test.StartTest();
		Object sumBalance = DueBalanceController.sumBalance(acct.Id);
        System.assertNotEquals(null,sumBalance);
    Test.StopTest();
        
	}
}