System.DmlException: Insert failed. First exception on row 0; first error: MIXED_DML_OPERATION, DML operation on setup object is not permitted after you have updated a non-setup object (or vice versa): Account, original object: User: []

@isTest
//Created by Matt - March 2016
//Designed for the Acorn Release
//

public class Test_Session_and_Session_Benefit {
    @testSetup static void setupTestData(){
        
        Test.startTest(); 
        List<User>testUsers = new List<User>();
        
        //Create Admin User
        Profile p = [SELECT Id FROM Profile WHERE Name='System Administrator']; 
        testUsers.add(new User(Alias = 'SysAdmin', Email='admin@bcinsourcing.com', 
                          EmailEncodingKey='UTF-8', LastName='Testing', LanguageLocaleKey='en_US', 
                          LocaleSidKey='en_US', TimeZoneSidKey='America/Los_Angeles', ProfileId = p.Id, 
                          UserName='admin@bcinsourcing.com'));

         //Create Manager
        Profile pM = [SELECT Id FROM Profile WHERE Name='BCS Manager']; 
        testUsers.add(new User(Alias = 'TSTMGR', Email='testmanager@bcinsourcing.com', 
            EmailEncodingKey='UTF-8', LastName='TSTMGR', LanguageLocaleKey='en_US', 
            LocaleSidKey='en_US', TimeZoneSidKey='America/Los_Angeles', ProfileId = pM.Id, 
            UserName='testmanager@bcinsourcing.com'));

        //Create Standard User
        Profile pS = [SELECT Id FROM Profile WHERE Name='Chatter Only - BCS Standard']; 
        testUsers.add(new User(Alias = 'TSTBCS', Email='TSTBCS@bcinsourcing.com', 
            EmailEncodingKey='UTF-8', LastName='TSTBCS', LanguageLocaleKey='en_US', 
            LocaleSidKey='en_US', TimeZoneSidKey='America/Los_Angeles', ProfileId = pS.Id, 
            UserName='TSTBCS@bcinsourcing.com'));
        
        	Insert testUsers;
                 
        //Create Accounts
        List<Account> accounts = new List<Account>();
        for(Integer i=0;i < 2;i++){
            accounts.add(new Account(
                Name = 'Test Acc' +i,
                Account_Code__c = 'AC' +i,
                Type = 'Client',
                Niche__c = 'Services'
            ));
        }
        
        	insert accounts; 
        Test.stopTest();
 
        //Create Public Group
        List<Group> pubGroup = new List<Group>();
        for(Account acc:accounts){
            pubGroup.add(new Group(
                Name             = acc.Name,
                DeveloperName    = acc.Name,
                Type             = 'Regular'
             ));
        }
        
        	insert pubGroup;
        
        //Create Carriers
        List<Account> carriers = new List<Account>();
        for(Integer i=0;i < 2;i++){
            carriers.add(new Account(
                Name = 'Test Carrier' +i,
                Account_Code__c = 'CA' +i,
                Type = 'Carrier'
            ));
        }
        insert carriers;
        
        //Create Hub
        List<BCS__c> theHub = new List<BCS__c>();
        for(Integer i=0;i < 1;i++){
            theHub.add(new BCS__c(
                Name = testUsers.get(0).LastName,
                DOH__c = Date.today().addDays(2),
                User__c = testUsers.get(0).Id
            ));
        }
        insert theHub;
        
        //Create Benefit Masters
        List<Benefit_Master__c> benMasters = new List<Benefit_Master__c>();
        for(Account car:carriers){
            for(Integer i=0;i < 2;i++){
                benMasters.add(new Benefit_Master__c(
                    Name = 'BenMaster'+i,
                    Carrier__c = car.Id
                ));
            }
        }
        insert benMasters;
        
        //Create Account Benefits
        List<Account_Benefit__c> AccBenefit = new List<Account_Benefit__c>();
        for(Benefit_Master__c master:benMasters){
            for(Integer i=0;i < 2;i++){
                AccBenefit.add(new Account_Benefit__c(
                    Name = master.Name,
                    Benefits_Master__c = master.id,
                    Account__c = accounts.get(i).Id,
                    Show_Elimination_Period__c   = false,
                    Show_Volume__c               = false
                ));
            }
        }
        insert AccBenefit;
        
        //Create Employees
        List<Employees__c> employee = new List<Employees__c>();
        for(Account acc:accounts){
            for(Integer i=0;i < 10;i++){
                employee.add(new Employees__c(
                    Name = acc.Account_Code__c + i, //Creates a HBS ID like AC11 and AC12
                    First_Name__c = 'First'+i,
                    Last_Name__c = 'Last'+i,
                    Account__c = acc.Id,
                    Review_End_Date__c = Date.today(),
                    DOH__c = Date.today(),
                    PayCy__c = 'Biweekly'
                ));
            }
        }
        insert employee;
    }
    
    
    //Create Acorn Sessions  
    static testMethod void testCreateSessions(){
        
        ....subsequent code redacted....
}