Error at run time: Variable does not exist: ProgramFlowExperiment.EmailCounter

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Running this example of a test class using a trigger fails when I get to the TestContactOwnerChange class. The EmailCounter variable is not visible and the System.assertEquals does not see the variable EmailCounter created in the ProgramFlowExperiment class. 

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public class ProgramFlowExperiment {

public static Integer EmailCounter = 0;

private void SendEmail(){
EmailCounter++;
System.Debug('Queueing the email to send');
}

private void SendQueuedEmails(){
System.Debug('Sending queued emails');
}

public void HandleContactUpdateTrigger(List<Contact> newlist, Map<Id, Contact> oldmap){
for(Contact ct: newlist){
if(ct.OwnerId != oldmap.get(ct.Id).OwnerId){
SendEmail();
}
}
SendQueuedEmails();
}
}

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trigger ContactOwnerChangeTrigger on Contact (after update) {
ProgramFlowExpermient pf = new ProgramFlowExperiment();
pf.HandleContactUpdateTrigger(trigger.new, trigger.oldmap);
}

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@isTest
private class TestContactOwnerChange {

static testMethod void TestOwnerChange() {
// Create some tests
List<Contact> newcontacts = initTextContacts('c', 5);

user u = initTestUser('myname', 'myname');

System.runAs(u){
//These contacts will be created with the fake user as owner
insert newcontacts;
}

Test.StartTest();
for(Contact ct: newcontacts){
ct.OwnerID = UserInfo.getUserId();
ct.Email = 'someone@somehwere.com';
}

update newcontacts;

Test.stopTest();

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

}

public static List<Contact> initTestContacts(String prfix, Integer count){
List<Contact> results = new List<Contact>();
for(Integer x=1; x <count; x++){
results.add(new Contact(LastName = prefix + '_' + string.valueOf(x),
email = prefix + '_' + string.valueOf(x) + '@apexfundamentals.com' ));
}
return results;
}

public static User initTestUser(String username, String thealias){
User u = new User(Alias = thealias,
Email = username + '@apexfunadamentals.com',
FirstName = 'Joe', LastName = username,
TimeZoneSidKey = 'America/Los_Angeles',
UserName = username + '@apexfundamentals.com',
UserPermissionsMarketingUser=true, LocaleSidKey='en_US',
EmailEncoding='UTF-8', LanguageLocaleKey = 'en_US');
u.ProfileID = userinfo.getProfileId();
return u;

}
}