Use of static variables in Apex Triggers and Unit Testing

Eg:

Trigger on a contact to send email when its owner changes.

It uses Apex class to handle the logic.

trigger ContactOwnerChangeTrigger on Contact (after update) {

ProgramFlowExperiment pf = new ProgramFlowExperiment();

//passing the new contact record after update

//and the old contact contact record before update

pf.HandleContactUpdateTrigger(trigger.new, trigger.oldMap);

}

public class ProgramFlowExperiment {

//to keep track of the email queued

public static Integer EmailCounter = 0;

private void SendEmail()

{

//every time an email is queued

//this counter is incremented

EmailCounter++;

System.Debug('Queueing email to send');

System.debug('total emails queued ' + emailcounter);

}

private void SendQueuedEmails()

{

System.Debug('Sending Email queue');

}

//this set id will collect the contact ids that are processed

//so that they are not processed again

private static Set<ID> AlreadyProcessedList = null;

public void HandleContactUpdateTrigger(List<Contact> newlist, Map<ID, Contact> oldmap)

{

//create an instance of the set variable - that collects processed contacts -

//only if its null

if(AlreadyProcessedList==null) AlreadyProcessedList = new Set<ID>();

for(Contact ct: newlist)

{

//first check that this contact record id is already processed

//if yes do not process further and move to the next record

if(AlreadyProcessedList.contains(ct.id)) continue;

//check if the contact owner has changed

if(ct.OwnerID != oldmap.get(ct.ID).OwnerID)

{

//changed contact owners need to be sent email

//store this record id in the set variable

AlreadyProcessedList.add(ct.id);

SendEmail();

}

}

SendQueuedEmails();

}

}

Unit Test:

@isTest

public class TestContactOwnerChange {

@TestSetup static void setUp(){

// Create some test contacts

List<Contact> newcontacts = initTestContacts('c', 5);

//create an initial user

User u = initTestUser('somebody', 'somebody');

System.runAs(u)

{

// These contacts will be created the owner Joe

insert newcontacts;

}

System.debug('initial contacts created with owner somebody');

}

public static List<Contact> initTestContacts(String prefix, Integer count)

{

List<Contact> results = new List<Contact>();

for(Integer x=0; x<count; x++)

{

results.add(new Contact(LastName = prefix + '_' + string.ValueOf(x),

email = prefix + '_'+string.ValueOf(x)+'@apexfundementals.com'));

}

return results;

}

public static User initTestUser(String username, String thealias)

{

User u = new User(Alias = thealias,

Email = username + '@apexfundementals.com',

FirstName='Joe', LastName= username,

TimeZoneSidKey = 'America/Los_Angeles',

UserName = username + '@apexfundementals.com',

UserPermissionsMarketingUser=true, LocaleSidKey='en_US',

EmailEncodingKey='UTF-8', LanguageLocaleKey = 'en_US');

u.ProfileID = userinfo.getProfileId();

return u;

}

@isTest static void TestOwnerChange() {

List<Contact> newcontacts = [select ownerID, email from contact];

Test.StartTest();

//retrieve each contact record

//and change their owner to the current owner and email

for(Contact ct: newcontacts)

{

ct.OwnerID = UserInfo.getUserId();

System.debug('owner change to ' + ct.OwnerID);

ct.Email = 'someone@somewhere.com';

}

update newcontacts;

Test.StopTest();

System.AssertEquals(newcontacts.size(), ProgramFlowExperiment.EmailCounter);

}

}