I'm curious if anybody knows why I'm getting the error in the subject of this thread?  ^^^

test.starttest();

Profile p = [SELECT Id FROM profile WHERE name='API'];
User u1 = new User(alias = 'newUser', email='user@domain.com',
emailencodingkey='UTF-8', lastname='Testing', languagelocalekey='en_US',
localesidkey='en_US', profileid = p.Id,
timezonesidkey='America/Los_Angeles', username='user@domain.com');

insert u1;

system.debug('###### the user is: ' + u1.Id);

System.runAs(u1)
{

List<Opportunity> opptys = new List<Opportunity>();

Opportunity o1 = new Opportunity();
o1.Name = 'Test Oppty 1';
o1.CloseDate = Date.today();
o1.StageName = 'Reservation';
o1.Rental_Rate__c = 100;
opptys.add(o1);

Opportunity o2 = new Opportunity();
o2.Name = 'Test Oppty 2';
o2.CloseDate = Date.today();
o2.StageName = 'Appointment';
opptys.add(o2);

Opportunity o3 = new Opportunity();
o3.Name = 'Test Oppty 3';
o3.CloseDate = Date.today();
o3.StageName = 'Lead';
opptys.add(o3);


insert opptys;

system.debug('##### the opportunities are: ' + opptys);
system.debug('##### created by: ' + opptys[0].CreatedById);

}

test.stopTest();