Hi All,

I am new to Apex triggers. Could you please help me with an issue I have with my test class?
I have a Master-Child relationship between Person account and a custom object called Staff_and_duty_travel__c (Person account being the master), but I am not always sure I'll have a value in the Associated_account__c field of Staff_and_duty_travel__c.
Therefore, I wrote an Apex Trigger before insert on this object.

The Trigger checks if there is a value in Associated_account__c.
If not, it uses the field Staff_email_address__c of the record to search in the emails fields of the Person Accounts (Customer_Email__pc and Secondary_Email__pc) if an account already exists with this email.
If yes, it gives the id of this account to the field Associated_account__c.
If not, it creates the account with the values contained in the record and it gives the id of this new account to the field Associated_account__c.

The trigger seems to work fine (I created several records to test every scenario), but my Test class fails.

Here is my trigger:

trigger SDT_Master_Child_Relation on Staff_and_duty_travel__c (before insert) {
    
    Set<String> staffEmailAdress = new Set <String> ();
    List<Account> accountsList = new List<Account> ();
    Id assocAccountId;
    RecordType personAccountRecordType =  [SELECT Id FROM RecordType WHERE Name = 'Person Account' and SObjectType = 'Account' Limit 1];

    
    //We create the list of all the email adresses from the bookings that are inserted
    for (Staff_and_duty_travel__c Travel : Trigger.New)
    {
        staffEmailAdress.add(Travel.Staff_email_address__c);
    }
    
    //We create the list of all the accounts containing one of the emails from the bookings that are inserted
    for(Account acc :[select Id, Customer_Email__pc, Secondary_Email__pc from Account where Customer_Email__pc IN:staffEmailAdress OR Secondary_Email__pc IN:staffEmailAdress])
    {
               accountsList.add(acc);
    }
        
   
    //For every booking that is inserted, we associate an account.
    for (Staff_and_duty_travel__c Travel : Trigger.New)
    {
        assocAccountId=Null;
        
        //We check if an account is already associated
        assocAccountId=Travel.Associated_account__c;
        
        //If not, we associate one.
        If (assocAccountId==Null){
            
            //We check if an account with the Staff email exists
            for (Account acc2 : accountsList){
                if(acc2.Customer_Email__pc.equals(Travel.Staff_email_address__c) || acc2.Secondary_Email__pc.equals(Travel.Staff_email_address__c)) {
                    assocAccountId=acc2.Id;
                }
            }
            //If not, we create thew account
            if (assocAccountId==Null){
                //Create the account
                Account newPersonAccount = new Account();
                newPersonAccount.FirstName = Travel.Staff_First_Name__c;
                newPersonAccount.LastName = Travel.Staff_Last_name__c;
                newPersonAccount.Customer_Email__pc = Travel.Staff_email_address__c;
                newPersonAccount.PersonHomePhone=Travel.Staff_phone_number__c;
                newPersonAccount.RecordTypeId = personAccountRecordType.Id;
                insert newPersonAccount;
                assocAccountId=newPersonAccount.Id;
            }
        }
        //We associate the account
        Travel.Associated_account__c=assocAccountId;
    }
    
}

Here is my Test class (I have put in bold the assertions that fail):
 

@isTest

public class SDT_Master_Child_Relation_Test {
    
    
    static testMethod void testAssociateAccount(){
        RecordType personAccountRecordType =  [SELECT Id FROM RecordType WHERE Name = 'Person Account' and SObjectType = 'Account' Limit 1];
        
        //Create a test account
        Account accTest=new Account (RecordTypeId = personAccountRecordType.Id,
                                     FirstName='Test',
                                     LastName='TestAccountTrigger', 
                                     Customer_Email__pc='testFirstEmail@trigger.com',
                                     Secondary_Email__pc='testSecondEmail@trigger.com');
        insert accTest;
        
        //Create four travels to test the four possibilities
        Staff_and_duty_travel__c travelTest1=new Staff_and_duty_travel__c (Staff_Last_name__c='AccountAlreadyAssociated', 
                                                                           Staff_First_Name__c='TestTrigger',
                                                                           Staff_phone_number__c='0486786',
                                                                           Staff_email_address__c='testNoEmail@trigger.com',
                                                                           Associated_account__c=accTest.Id);
        Staff_and_duty_travel__c travelTest2=new Staff_and_duty_travel__c (Staff_Last_name__c='FirstEmail', 
                                                                           Staff_First_Name__c='TestTrigger',
                                                                           Staff_phone_number__c='0486786',
                                                                           Staff_email_address__c='testFirstEmail@trigger.com');
        Staff_and_duty_travel__c travelTest3=new Staff_and_duty_travel__c (Staff_Last_name__c='SecondEmail', 
                                                                           Staff_First_Name__c='TestTrigger',
                                                                           Staff_phone_number__c='0486786',
                                                                           Staff_email_address__c='testSecondEmail@trigger.com');
        Staff_and_duty_travel__c travelTest4=new Staff_and_duty_travel__c (Staff_Last_name__c='ThirdEmail', 
                                                                           Staff_First_Name__c='TestTrigger',
                                                                           Staff_phone_number__c='0486786',
                                                                           Staff_email_address__c='testThirdEmail@trigger.com');
        
        List<Staff_and_duty_travel__c> travels = new List<Staff_and_duty_travel__c>{travelTest1, travelTest2, travelTest3, travelTest4};
        
        //Run the test
        Test.startTest();
        insert travels;
        Test.stopTest();

        //We check for each of the travels if the account has been associated
        //For travelTest1:
        System.assert(travelTest1.Associated_account__c==accTest.Id);
        
        //For travelTest2:
        System.assert(travelTest2.Associated_account__c==accTest.Id);
        
        //For travelTest3:
        System.assert(travelTest3.Associated_account__c==accTest.Id);
        
        //For travelTest4, we have to check if an account has been created with the right values, then if it has been associated to the travel:
        Account accTest4=[select Id, FirstName,LastName,PersonHomePhone
                         from Account
                         where RecordTypeId = :personAccountRecordType.Id and Customer_Email__pc=:travelTest4.Staff_email_address__c ];
        System.assert(accTest4.FirstName==travelTest4.Staff_First_Name__c);
        System.assert(accTest4.LastName==travelTest4.Staff_Last_name__c);
        System.assert(accTest4.PersonHomePhone==travelTest4.Staff_phone_number__c);
        System.assert(travelTest4.Associated_account__c==accTest4.Id);   
    }
}

I get the "System.AssertException: Assertion Failed" error for the assertion I have put in bold.
I don't understand where is the problem coming from, so any help is appreciated.
Regards,
Constance Rouge