I've got an after insert\after update trigger running off the Account object which is upsertting a new child record (object name : "SubsidiariesAndBrands__c"). It's running fine, but for some reason I can't get this test class to work properly. 

Here is the whole test class : 

public with sharing class AutoCreateSubsOnAccountTriggerTest {

    static testMethod void testAutoCreateSubsOnAccountTriggerTest() {
        // Set up test User.
        User testUser = generateTestUser();

        // Generate Account
        Account acc = new Account(Name = testUser.Id);
 
        // Start test and insert sub
        Test.startTest();
        insert acc;
        Test.stopTest();

        // Get the subs from the DB to ensure they were created
        List<SubsidiariesAndBrands__c> subs = [SELECT
                                                 Id
                                             FROM
                                                 SubsidiariesAndBrands__c
                                             WHERE
                                                 Parent_Account__c = :acc.Id
        ];

        // There should be 1 sub
        System.assert(1 == subs.size(), 'One sub object is expected');
    }

    private static User generateTestUser(){
        // using the System Admin profile because it will always be there
        Profile sysAdmin = [SELECT 
                               Id 
                            FROM 
                               Profile 
                            WHERE 
                               Name = 'System Administrator'
                            LIMIT 1
        ];
 
        // Generate the user
        User newUser = new User(
            UserName = 'unit.tester@example.com',
            LastName = 'Test',
            FirstName = 'Jane',
            CompanyName = 'TestCo',
            Title = 'Developer',
            Email = 'unit.tester@example.com',
            ProfileId = sysAdmin.Id,
            emailencodingkey = 'UTF-8',
            languagelocalekey = 'en_US',
            localesidkey = 'en_US',
            timezonesidkey = 'America/Los_Angeles'
        );

        // Insert that user
        insert newuser;

        return newuser;
    }
}

 It's error-ing out on the line I underlined, with the error message of : "System.AssertException: Assertion Failed: One sub object is expected"

I guess for some reason the sub record isn't being created. I can't figure out why. 

Here is the actual trigger if you need it : 

trigger AutoCreateSubOnAccount on Account (after insert, after update) {
         public string type{get;set;}
List <SubsidiariesAndBrands__c> subToInsert = new List <SubsidiariesAndBrands__c> ();
      
    for (Account o : Trigger.new) { 
         
        type = o.Auto_Formula_Record_Type__c;
          System.debug('xxx type string xxx ' + type );
                   
        SubsidiariesAndBrands__c v = new SubsidiariesAndBrands__c (); //instantiate the object to put values for future record
        
                  
        v.Parent_Account__c= o.id; 
        v.Name = o.Name;
        v.SubName__c = o.Name;
        v.Industry__c = o.Industry; 
        v.Subsidary_Brand_Account_Number__c = o.Account_Number__c;
        v.ParentRecName__c = type;
                
        subToInsert.add(v);
      
    }
    
    try {
       if (type == 'Ultimate Parent') 
        upsert subToInsert SubName__c; 
    } catch (system.Dmlexception e) {
        system.debug (e);
    }
    
}

Thank you very much for your help and input.