Dear All,

I was trying to write test class for my trigger, but it it giving me error like below
'FATAL_ERROR System.DmlException: Insert failed. First exception on row 0; first error: CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY, restrictCase: execution of BeforeInsert' , 'FATAL_ERROR caused by: System.NullPointerException: Attempt to de-reference a null object'

heres my trigger

trigger restrictCase on Case(before insert)
{
MaxCase__c mxx = MaxCase__c.getInstance('MaxValue');    
Integer mvv = Integer.valueOf(mxx.Max__c);
    system.debug('int value' + mvv);

Set<Id> userIds = new Set<Id>();

    
for (case cc : Trigger.new)  
{
userIds.add(cc.ownerId);
} 
 
List<User> userss = [Select Id, Name from User where Id in :userIds];  
Map<Id, Integer> userCases = new Map<Id,Integer>(); 
    
for (user u : userss)
{
 integer countCase = [Select count() from Case where ownerId=:u.Id AND createdDate = This_Month];
 userCases.put(u.id, countCase); 
 system.Debug('user and case' + u.Name + ' . ' + countcase);
}
  
for (case c : trigger.new)    
{

Integer countc = userCases.get(c.OwnerId);    
system.debug('current user case count' + countc);    
    if (countc > mvv)
    {
        c.addError('Too many cases created this month for user' + c.owner.Name + '(' + c.OwnerId + ')' + ':' + mvv);
    }
    
}   
    
    
    
}

and heres the test class I've written
 

@isTest

public class testRestrictCase {

 static testMethod void caseCreation1 ()
 {
          MaxCase__c maxi = new MaxCase__c();
     maxi.Name = 'newMax';
     maxi.Max__c = 80;
     insert maxi;
     
     system.debug('maxi custom setting' + maxi.Name);
     Integer maxiInt = Integer.valueOf(maxi.Max__c);
      system.debug('max value' + maxiInt);
     
     
  Account acct = new Account(Name='anamika');   
  insert acct;
     system.debug('account inserted' + acct.name);
 Contact con = new Contact(FirstName='aa', LastName='bb', AccountId=acct.Id, email='abc@g.com');
  insert con;
     system.debug('contact inserted' + con.name);

 List<Case> casess = new List<Case>();
     for(integer i = 0; i<maxiInt ; i++)
     {
    Case TestC = new Case(Subject='Test Controller Acct Case'+ i, accountId=acct.id, status='New', origin ='Email', contactId=con.id, priority='Medium', type='Mechanical', reason='Installation');
     casess.add(Testc); 
system.debug('testC .i.' + TestC.Subject);
 }
   insert casess;
     system.debug('cases size' + casess.size());
     
     Case TestC1 = new Case(Subject='Test Controller Acct Case new', accountId=acct.id, status='New', origin ='Email', contactId=con.id, priority='Medium', type='Mechanical', reason='Installation');

     try{
         insert TestC1;
     }
 catch(DMLException ex)
 {
   system.debug('max cases inserted');  
 }
 
 }
}

​Please help me finding the issue.

Thanks a lot in advance.