@isTest
public class WE_OppUpdatesTest{

    @testSetup
    static void dataSetup() {

        Profile p1 = [SELECT Id FROM Profile WHERE Name = 'System Administrator - Wex Europe'];

        User[] userList = new User[]{};
            User u = new User();

        u.FirstName = 'Alex';
        u.LastName = 'Sherwood';
        u.Email = 'test@wexeurope.com';
        u.Username = 'astest@wexeurope.com';
        u.Alias = 'astest';
        u.ProfileId = p1.Id;
        u.TimeZoneSidKey    = 'America/Denver';
        u.LocaleSidKey      = 'en_US';
        u.EmailEncodingKey  = 'UTF-8';
        u.LanguageLocaleKey = 'en_US';
        userList.add(u);

        system.debug('u contains ' + u);

        insert userList;

        System.runas(u){

            WEID__c[] csList = new WEID__c[]{};
                WEID__c cs = New WEID__c();
            cs.Name = 'CP Virtual Prepaid MC';
            cs.WEOppId__c = '012700000005qif';

            csList.add(cs);

            insert csList;
            system.debug('csList contains ' + csList);

            //create Target records
            Target__c[] targetList = new Target__c[]{};
                Target__c t = new Target__c();

            t.Name = 'Jun Test';
            t.OwnerId = u.Id;
            t.Salesperson__c = u.Id;
            t.Team__c = 'Virtual Sales EU';
            t.Year_End_Date__c = Date.newInstance(2015,12,31);
            t.Target__c = 100000;
            t.Month_End_Date__c = Date.newInstance(2015,06,30);
            targetList.add(t);

            Target__c t1 = new Target__c();
            t1.Name = 'Jul Test';
            t1.OwnerId = u.Id;
            t1.Salesperson__c = u.Id;
            t1.Team__c = 'Virtual Sales EU';
            t1.Year_End_Date__c = Date.newInstance(2015,12,31);
            t1.Target__c = 100000;
            t1.Month_End_Date__c = Date.newInstance(2015,07,30);
            targetList.add(t1);

            Target__c t2 = new Target__c();
            t2.Name = 'Jul 16 Test';
            t2.OwnerId = u.Id;
            t2.Salesperson__c = u.Id;
            t2.Team__c = 'Virtual Sales EU';
            t2.Year_End_Date__c = Date.newInstance(2016,12,31);
            t2.Target__c = 100000;
            t2.Month_End_Date__c = Date.newInstance(2016,07,30);
            targetList.add(t2);

            insert targetList;

        }
    }

    static testMethod void testOppsPt1(){

        List<Opportunity> immOpportunitys = new List<Opportunity>();
        for (Integer i = 0; i < 1; i++) {

            Opportunity o = new Opportunity();
            o.name = 'Test Opp' + i;
            o.RecordTypeId = '012700000005qif';

/*ERROR >*/ o.OwnerId = u.Id;
            o.Ramp_Profile__c = 'Immediate';
            o.StageName = '1) Suspect';
            o.CloseDate = date.newInstance(2015,06,15);
            o.Monthly_Txn_Revenue_POS__c = 0;
            o.Annual_transaction_volume__c = 1000;
            o.Credit_Limit__c = 100.00;
            o.Date_Credit_Limit_Approved__c = date.newInstance(1901, 01, 01);
            o.Payment_Terms_Days__c = 5;
            o.Billing_Cycle__c = 'Daily';
            o.Annual_Settlement_Value__c = 100.00;
            o.Average_transaction_Value_POS__c = 1.00;

            immOpportunitys.add(o);
        }
        insert immOpportunitys;

    }
}

static testMethod void testOppsPt1(){
    User u = [select Id from User where Username = 'astest@wexeurope.com'];
    List<Opportunity> immOpportunitys = new List<Opportunity>();
    for (Integer i = 0; i < 1; i++) {
        ...
}

@isTest
public class WE_OppUpdatesTest {

   @testSetup
   static void dataSetup() {
      ...
      insert user;
   }

   static void additionalDataSetup() {
      User u = [SELECT Id FROM User WHERE Name = 'yourname' LIMIT 1];
      System.runAs(u) {
         ... insert all additional records
      }
   }

   static testMethod void test_something() {
      additionalDataSetup();
      ...
   }

   static testMethod void test_somethingElse() {
      additionalDataSetup();
      ...
   }
}