Hi, I am new to SalesForce Development. I wrote a trigger and a test class for it. Below is the code for the test class. When I execute the test class I get System.QueryException: List has no rows for assignment to SObject. First I thought I had some problem with my query but I executed it using Query Editor and the record returned successfully. I would appreciate if you can help me with this.

@isTest
private class NumberOfAttendeesUpdateTestClass{

    static testMethod void validateNumberOfAttendeesUpdate(){
   
        Contact ctc = new Contact(FirstName='Test',LastName='Contact', Conference__c='a00o0000003jzAwAAI');
        Conference__c cfc = [SELECT Id, Name, Number_of_Attendees__c from Conference__c WHERE Id = 'a00o0000003jzAwAAI' LIMIT 1];
        Double na = cfc.Number_of_Attendees__c;
        System.debug('Number of Attendees in Conference ' + cfc.Name + ' before inserting ' + cfc.Number_of_Attendees__c);
       
        insert ctc;
       
        cfc = [SELECT Id, Name, Number_of_Attendees__c from Conference__c WHERE Id = 'a00o0000003jzAwAAI' LIMIT 1];
        System.debug('Number of Attendees in Conference ' + cfc.Name + ' before inserting ' + cfc.Number_of_Attendees__c);
       
        System.assertEquals(na, na + 1);
   
    }
}