Hi Bob,

Your testing methods are definitely correct (if you use the Salesforce UI). 

You will see that the code fails if you do the following:

In your test class:
1: create 3 leads with 3 different Type__c values
2: add those 3 leads to a list
3: insert the list

4: create 3 tasks, 1 for each lead (don't insert them yet!)
5: Add the 3 tasks to a list
6: Insert the list.

You will now see that all 3 tasks have the same Account_Type__c value.

Here's the code to do so (I adjusted the test class from previous post):
 

@IsTest
private Class TestAcountType {

  static testmethod void insertTask() {
    //create test data

    Lead l = new Lead(LastName = 'LastName1', Company = 'Company1', Type__c = 'Some Type');
    insert l;

    //Query the just created lead again to get Id
    List<Lead> leads = [Select Id, Name, Company, Type__c From Lead WHERE Company = 'Company1'];
    Lead lead1 = leads.get(0);

    Test.startTest();

    Task t = new Task();
    t.WhoId = lead1.Id;
    t.Type = 'Other';
    insert t;

    Test.stopTest();

  }

  static testmethod void testInsertMultipleTasks(){
    //create test data

    List<Lead> leadsToInsert = new List<Lead>();
    Lead lead1 = new Lead(LastName = 'LastName1', Company = 'Company1', Type__c = 'Type1');
    Lead lead2 = new Lead(LastName = 'LastName2', Company = 'Company2', Type__c = 'Type2');
    Lead lead3 = new Lead(LastName = 'LastName3', Company = 'Company3', Type__c = 'Type3');
    leadsToInsert.add(lead1);
    leadsToInsert.add(lead2);
    leadsToInsert.add(lead3);

    insert leadsToInsert;

    //Query the just created leads again to get Id
    List<Lead> leads = [Select Id, Name, Company, Type__c From Lead];

    //Make sure all 3 leads are created
    system.assertEquals(3, leads.size(), 'There should be three leads in the database');

    Lead lead1fromDb = leads.get(0);
    Lead lead2fromDb = leads.get(1);
    Lead lead3fromDb = leads.get(2);

    Test.startTest();

    List<Task> tasksToInsert = new List<Task>();

    Task task1 = new Task(WhoId = lead1fromDb.Id, Type = 'Other');
    Task task2 = new Task(WhoId = lead2fromDb.Id, Type = 'Other');
    Task task3 = new Task(WhoId = lead3fromDb.Id, Type = 'Other');

    tasksToInsert.add(task1);
    tasksToInsert.add(task2);
    tasksToInsert.add(task3);

    insert tasksToInsert;

    Test.stopTest();

    system.debug('Task1 Account_Type__c: ' + Task1.Account_Type__c);
    system.debug('Task2 Account_Type__c: ' + Task1.Account_Type__c);
    system.debug('Task3 Account_Type__c: ' + Task1.Account_Type__c);

    system.assertEquals(lead1fromDb.Type__c, task.Account_Type__c, 'Task1 Account Type must match Lead1 Type__c');
    system.assertEquals(lead2fromDb.Type__c, task.Account_Type__c, 'Task2 Account Type must match Lead2 Type__c');
    system.assertEquals(lead3fromDb.Type__c, task.Account_Type__c, 'Task3 Account Type must match Lead3 Type__c');

  }

}

You will find that the code fails at the assertions at the end. If you check the debug logs, you will see that all 3 tasks have the same Account_Type__c value.

This has to do with bulkifying your code (best practice: Always bulkify everything). As long as people use the Salesforce UI, it will keep on working. But try loading a bunch of tasks via the data loader. There will be 200 records at the same time inserted in Salesforce (and hitting your trigger. Those records will be in Trigger.new). That's when the code will fail.

But hey, since you're not a coder, I don't expect you to know that. You did a great job! It's just a tip from my side to prevent corrupt records when someone loads a buch of tasks using the API's (e.g. via the Data loader).

Keep up the good work! And if you run into issues, you know where to find the community :-)

Happy coding!

Regards,
Martijn Schwärzer