its my Trigger

// this trigger used and sum of the contact on the account object
trigger countcontacts on Contact (after insert, after delete) {
    Set<Id> aId = new Set<Id>();
    
    if(Trigger.isInsert){
        System.debug('Insert contact for trigger.new - '+Trigger.New);
        for(Contact opp : Trigger.New){
            aId.add(opp.AccountId);
        }
        List<Account> acc = [select id,sum_of_the_contact__c from Account where Id in:aId];
        List<Contact> con = [select id from contact where AccountId in :aId];
        
        for(Account a : acc){
            a.sum_of_the_contact__c=con.size();
        }
        update acc;
        System.debug('Number is '+acc);
    }
    
    if(Trigger.isDelete){
        System.debug('delete contact for trigger.old - '+Trigger.Old);
        for(Contact opp : Trigger.old){
            aId.add(opp.AccountId);
        }
        List<Account> acc = [select id,sum_of_the_contact__c from Account where Id in:aId];
        List<Contact> con = [select id from contact where AccountId in :aId];
        
        for(Account a : acc){
            a.sum_of_the_contact__c=con.size();
            
        }
        update acc;
        System.debug('Number is '+acc);
    }
    }
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    its my test class but only covred 58% how to 100% please slove
    
    
    @isTest
public class countcontacts_Test{
    @isTest
    static void tesMethodss()
    {
        account ac=new account(name='test');
        insert ac;
        
        contact cont=new contact(lastName='test',firstName='test', Accountid=ac.Id);
        insert cont;
      
        
    }
}
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