Test data returning Null

Question

Test data creation:

Account acct = new Account(Name='TestAccount', Field__c='TestInfo');
    insert acct;

Contact con = new Contact(FirstName = 'TestFname1',LastName = 'TestLname1', Email = '[email protected]', 
                              AccountId = acct.Id);
    insert con; 
Profile p = [SELECT Id FROM Profile WHERE Name = 'Custom Profile'];
User u = new User(/* Standard and Custom fields*/, ContactId = con.Id);

System.debug('user.contactId: ' +u.ContactId);
System.debug('user.con.FirstName: ' +u.Contact.FirstName);

I can able to get the ContactId, but not the FirstName. How to get the Firstname and other fields(User.Contact.Account.Name)?

I tried to query: Select Contact.FirstName from User which is working as expected, but why I cannot get this in my test data?

Answer 1

You have created an instance of the user. Insert user record and separately perform SOQL query to retrieve Contact.FirstName

Account acct = new Account(Name='TestAccount', Field__c='TestInfo');
    insert acct;

Contact con = new Contact(FirstName = 'TestFname1',LastName = 'TestLname1', Email = '[email protected]', 
                              AccountId = acct.Id);
    insert con; 
Profile p = [SELECT Id FROM Profile WHERE Name = 'Custom Profile'];
User u = new User(/* Standard and Custom fields*/, ContactId = con.Id);
insert u;    

System.debug('user.contactId: ' +u.ContactId);

//retrieve user record by SOQL
User userObj = [SELECT Contact.FirstName FROM User WHERE Id =:u.Id];

System.debug('user.con.FirstName: ' +userObj.Contact.FirstName);