Why is System Assert returning wrong value (Trigger & Test Class)?

Question

Context: I am trying to build a dupe counter that counts how many Leads match based on the Email value field. Here is the trigger:

//Look for duplicate contacts based on email
//Populate a Dupe_Lead_Counter__c field with a number value if >0 matches found
trigger CountDupeLeads on Lead (before insert, before update) {
    for (Lead l : Trigger.new) {
        //Make sure our lead has an email address
        if (l.Email != null) {
            //Find a dupe
            String leadEmail = l.Email;
            List<Lead> dupeLeads = [SELECT Id FROM Lead WHERE Email = :leadEmail];

            //If a dupe is found, update a field
            if (dupeLeads.size() > 0) {
                l.Dupe_Lead_Counter__c = dupeLeads.size();
            } else {
                //0 would designate a true unique
                l.Dupe_Lead_Counter__c = 0;
            }
        //want 'null' to distinguish Leads disqualified from the lookup versus true uniques
        } else {
            l.Dupe_Lead_Counter__c = null;
        }
    }

}

I then created a @isTest class:

@isTest
public class TestCountingDupes {
    static testMethod void testDupeCounter() {
        //Principle #ls: Create recordsd from Scratch           

        Lead dupeLead1 = new Lead();
        dupeLead1.FirstName = 'Peter';
        dupeLead1.LastName = 'Parker';
        dupeLead1.Email = 'spiderman@gmail.com';
        dupeLead1.Company = 'Tryler McTrevor Inc';
        insert dupeLead1;

        Lead dupeLead2 = new Lead();
        dupeLead2.FirstName = 'Jane';
        dupeLead2.LastName = 'Seymour';
        dupeLead2.Email = 'spiderman@gmail.com';
        dupeLead2.Company = 'Tryler McTrevor TEST Inc';
        insert dupeLead2;

        //Principle #2 use  System.assertEquals()
        dupeLead1 = [SELECT Id, Dupe_Lead_Counter__c FROM Lead LIMIT 1];
        System.assertEquals(2, dupeLead2.Dupe_Lead_Counter__c);

        //Principle #3: test things that shouldn't work!
        dupeLead2.Email = 'janeseymour@gmail.com';
        update dupeLead2;

        dupeLead1 = [SELECT Id, Dupe_Lead_Counter__c FROM Lead LIMIT 1];
        System.assertEquals(0, dupeLead2.Dupe_Lead_Counter__c);
    }
}

and the latest error I get from running the test is this:

System.AssertException: Assertion Failed: Expected: 2, Actual: null Class.TestCountingDupes.testDupeCounter

Clearly my trigger logic is populating a null value in that field before the Update action (when it should be the number 2), but I am at a loss--is it the way my @isTest is constructed with Lead record inserts and then updates or is it a systemic issue with my Apex trigger?

Answer 1

The reason for the failure is this part:

dupeLead1 = [SELECT Id, Dupe_Lead_Counter__c FROM Lead LIMIT 1];
System.assertEquals(2, dupeLead2.Dupe_Lead_Counter__c);

You are asserting that dupeLead2 has a certain value, but querying for dupeLead1. I would just get a fresh Lead and forget about reassigning previously declared variables. You can do:

Lead leadWithDupeEmail = [Select Id, Dupe_Lead_Counter__c from Lead where Id = :dupeLead2.Id limit 1];   
System.assertEquals(2, leadWithDupeEmail.Dupe_Lead_Counter__c); 

As a general comment, queries in for loops are bad. See https://developer.salesforce.com/page/Best_Practice:_Avoid_SOQL_Queries_Inside_FOR_Loops

Answer 2

When you insert first lead, there won't be any dupes. So Dupe_Lead_Counter__c field in dupeLead1 will be 0.

When you insert the second lead, there is a dupe lead (only one as the trigger is on before) already present and trigger will update Dupe_Lead_Counter__c field in dupeLead2 as 1. It will never be 2.

Also query with specific lead id and check its Dupe_Lead_Counter__c field in assert statements like below.

    //Principle #2 use  System.assertEquals()
    dupeLead2 = [SELECT Id, Dupe_Lead_Counter__c FROM Lead where id =: dupeLead2.Id];
    System.assertEquals(1, dupeLead2.Dupe_Lead_Counter__c);

    //Principle #3: test things that shouldn't work!
    dupeLead2.Email = 'janeseymour@gmail.com';
    update dupeLead2;

    dupeLead2 = [SELECT Id, Dupe_Lead_Counter__c FROM Lead where id=: dupleLead2.Id];
    System.assertEquals(0, dupeLead2.Dupe_Lead_Counter__c);