Need help in test class for code coverage

Question

I have a requirement, where i need to populate all the related contacts in Account Object Detail Page with comma seperated. For Example : If I have Account1 and Contact1 and Contact2 are related to Account1. Then, in account object detail page, i have a text box named "Related Contacts" which will display Contact1, Contact2.

Below is the trigger for that --

 trigger totalContacts on Contact (after insert,after update) {
    Set<ID> setAccountIDs = new Set<ID>();
    for(Contact c : Trigger.new){
        setAccountIDs.add(c.AccountId);
    }

    List<Account> accounts = [Select ID, Name,(Select Name From Contacts)  From Account WHERE ID IN :setAccountIDs];
    for(Account a : accounts){
        String contactName = '';
        for(Contact c : a.Contacts){
            contactName +=c.Name+ ' ,';                      
        }
        a.Associated_Contacts__c =contactName;
    }
    update accounts;

}

I wrote the below test class and it covers only 60%, please guide me to cover 100% of the code

@isTest 
public class testtotalContacts{
    static testMethod void insertnewContact(){

    Account accountToCreate = new Account();
    accountToCreate.Name = 'Test Account';
    accountToCreate.AW_Expiration_date__c = System.today();
    insert accountToCreate;

    Contact contactToCreate1 = new Contact();
    contactToCreate1.FirstName = 'Test 1';
    contactToCreate1.LastName = 'Trigger test class 1';
    contactToCreate1.Email = 'krishnakumar1@gmail.com';
    contactToCreate1.Account = accountToCreate;
    insert contactToCreate1;

    Contact contactToCreate2 = new Contact();
    contactToCreate2.FirstName = 'Test 2';
    contactToCreate2.LastName = 'Trigger test class 2';
    contactToCreate2.Email = 'krishnakumar@gmail.com 2';
    contactToCreate2.Account = accountToCreate;
    insert contactToCreate2;


    }
}

Answer 1

After looking at your code, it should throw following error

SObject row was retrieved via SOQL without querying the requested field

You are not querying "Associated_Contacts__c" field in account query, but later updating it in the code. Update your query as below:

List<Account> accounts = [Select ID, Associated_Contacts__c Name,(Select Name From Contacts)  From Account WHERE ID IN :setAccountIDs];

Update your test class as

@isTest 
public class testtotalContacts{
static testMethod void insertnewContact(){

Account accountToCreate = new Account();
accountToCreate.Name = 'Test Account';
insert accountToCreate;

Contact contactToCreate1 = new Contact();
contactToCreate1.FirstName = 'Test 1';
contactToCreate1.LastName = 'Trigger test class 1';
contactToCreate1.Email = 'krishnakumar1@gmail.com';
contactToCreate1.AccountID = accountToCreate.id;
insert contactToCreate1;

Contact contactToCreate2 = new Contact();
contactToCreate2.FirstName = 'Test 2';
contactToCreate2.LastName = 'Trigger test class 2';
contactToCreate2.Email = 'krishnakumar@gmail.com';
contactToCreate2.AccountID = accountToCreate.id;
insert contactToCreate2;


}
}