Hi i am getting this error in my test class my code is::::::

@isTest (seeAllData = true)
private class testneedAccApproval
{
    static testMethod void myUnitTestON24PBA_Recall()
    {     
        test.startTest();

        Profile p = [SELECT Id FROM Profile WHERE Name = 'System Administrator'];
        User u1 = new User();
        u1.Email = 'email1@email.com';
        u1.Alias = 'Alias2';
        u1.TimeZoneSidKey = 'America/New_York';
        u1.LocaleSidKey = 'ca';
        u1.EmailEncodingKey = 'UTF-8';
        u1.ProfileId = p.id;
        u1.LanguageLocaleKey = 'en_US';
        u1.FirstName = 'firstname1';
        u1.LastName = 'lastname1';
        u1.username= 'username1@first.com';
        insert u1;

        User u2 = new User();
        u2.Email = 'email2@email.com';
        u2.Alias = 'Alias3';
        u2.TimeZoneSidKey = 'America/New_York';
        u2.LocaleSidKey = 'ca';
        u2.EmailEncodingKey = 'UTF-8';
        u2.ProfileId = p.id;
        u2.LanguageLocaleKey = 'en_US';
        u2.FirstName = 'firstname2';
        u2.LastName = 'lastname2';
        u2.username= 'username2@first.com';
        insert u2;

        Product2 p1 = new product2(name='unittest');
        insert p1;

        Pricebook2 stdPb = [select Id from Pricebook2 where isStandard=true limit 1];
        insert new PricebookEntry(pricebook2id = stdPb.id, product2id = p1.id,unitprice=1.0, isActive=true);

        Pricebook2 pb = new pricebook2(name='unittest');
        insert pb;

        PricebookEntry pbe = new PricebookEntry(pricebook2id=pb.id, product2id=p1.id,unitprice=20000.0, isActive=true);
        insert pbe;

        Account AcntRec = new Account(name = 'Acc', Type = 'Customer', Industry = 'Automotive',BillingCity = 'Avon', BillingCountry = 'USA', BillingPostalCode = '14414', BillingState = 'New York', BillingStreet = 'Wall St');
        insert AcntRec;
        
        Opportunity o = new Opportunity (pricebook2id = pb.id, Name = 'OwnerRoleTest #1',AccountId = AcntRec.Id, Stagename='Open', Closedate=Date.newInstance(2010,02,02),Country__c = 'USA');
        insert o;

        Opportunity op = [select id from Opportunity where Name like 'OwnerRoleTest #1'];
        Pricebook2 pb1 = [select id from Pricebook2 where Name like 'unittest'];
        PricebookEntry pbe1 = [select id from PricebookEntry where pricebook2id=:pb1.id];

        ON24_Contract__c c = new ON24_Contract__c(name = 'testopty', Client_Name__c = AcntRec.Id, Opportunity__c=o.Id, Sales_Representative_1__c = u1.Id, Sales_Representative_2__c = u2.Id, Status__c = 'Draft', Agreement_Type__c = 'Services Agreement', Region__c='EMEA');
        insert c;
        
        AcntRec.BillingCity = '';
        AcntRec.BillingCountry = '';
        AcntRec.BillingPostalCode = '';
        AcntRec.BillingState = '';
        AcntRec.BillingStreet = '';
        update AcntRec;
        
        Contract_Line_Item__c cli = new Contract_Line_Item__c(ON24_Contract__c = c.Id, CurrencyIsoCode = 'USD', Validation_Pool__c = 'Yes', Quantity__c=2, Sales_Price__c = 15000, Product__c = p1.Id);
        insert cli;
        
        update c;
        
        approvalNeedAccountAdd vde = new approvalNeedAccountAdd();
        Pagereference pr = vde.closePopup();
        vde.isNotApproved = true;
        vde.displayPopUp = true;
        vde.displayApprovalPopUp = false;

    }
    static testMethod void myUnitTestON24PBA_Recall1()
    {     
 

        Profile p = [SELECT Id FROM Profile WHERE Name = 'System Administrator'];
        User u1 = new User();
        u1.Email = 'email1@email.com';
        u1.Alias = 'Alias2';
        u1.TimeZoneSidKey = 'America/New_York';
        u1.LocaleSidKey = 'ca';
        u1.EmailEncodingKey = 'UTF-8';
        u1.ProfileId = p.id;
        u1.LanguageLocaleKey = 'en_US';
        u1.FirstName = 'firstname1';
        u1.LastName = 'lastname1';
        u1.username= 'username1@first.com';
        insert u1;

        User u2 = new User();
        u2.Email = 'email2@email.com';
        u2.Alias = 'Alias3';
        u2.TimeZoneSidKey = 'America/New_York';
        u2.LocaleSidKey = 'ca';
        u2.EmailEncodingKey = 'UTF-8';
        u2.ProfileId = p.id;
        u2.LanguageLocaleKey = 'en_US';
        u2.FirstName = 'firstname2';
        u2.LastName = 'lastname2';
        u2.username= 'username2@first.com';
        insert u2;

        Product2 p1 = new product2(name='unittest');
        insert p1;

        Pricebook2 stdPb = [select Id from Pricebook2 where isStandard=true limit 1];
        insert new PricebookEntry(pricebook2id = stdPb.id, product2id = p1.id,unitprice=1.0, isActive=true);

        Pricebook2 pb = new pricebook2(name='unittest');
        insert pb;

        PricebookEntry pbe = new PricebookEntry(pricebook2id=pb.id, product2id=p1.id,unitprice=20000.0, isActive=true);
        insert pbe;

        Account AcntRec = new Account(name = 'Acc', Type = 'Customer', Industry = 'Automotive',BillingCity = 'Avon', BillingCountry = 'USA', BillingPostalCode = '14414', BillingState = 'New York', BillingStreet = 'Wall St');
        insert AcntRec;
        
         Contact con = new Contact(AccountId = AcntRec.Id, LastName = 'Charles', LeadSource = 'Web Services');
        insert con;

        Opportunity o = new Opportunity (pricebook2id = pb.id, Name = 'OwnerRoleTest #1',AccountId = AcntRec.Id, Stagename='Open', Closedate=Date.newInstance(2010,02,02),Country__c = 'USA');
        insert o;

        Opportunity op = [select id from Opportunity where Name like 'OwnerRoleTest #1'];
        Pricebook2 pb1 = [select id from Pricebook2 where Name like 'unittest'];
        PricebookEntry pbe1 = [select id from PricebookEntry where pricebook2id=:pb1.id];
        
        ON24_Contract__c c = new ON24_Contract__c(name = 'testopty1', Client_Name__c = AcntRec.Id, Opportunity__c=o.Id, Sales_Representative_1__c = u1.Id, Sales_Representative_2__c = u2.Id, Status__c = 'Draft', Agreement_Type__c = 'Services Agreement', Region__c='EMEA',Client_Type__c='Full Service',Vertical__c='Channel',Expiration_Date__c=Date.newInstance(2010,02,02),Effective_Date__c=Date.newInstance(2010,02,02),   Billing_Terms__c='Custom',Payment_Terms__c='Net 45');
        insert c;

        Contract_Line_Item__c cli = new Contract_Line_Item__c(ON24_Contract__c = c.Id, CurrencyIsoCode = 'USD', Validation_Pool__c = 'Yes', Quantity__c=2, Sales_Price__c = 15000, Product__c = p1.Id);
        insert cli;
        
        update c;
        
        approvalNeedAccountAdd vde = new approvalNeedAccountAdd();

             test.startTest();
            Pagereference pr = vde.submitAndProcessApprovalRequest() ;
            
            Approval__c AP1 = new Approval__c(Contract__c = c.Id);
            insert AP1;
            Approval__c AP = [select id from Approval__c where Contract__r.Status__c = 'Draft'];    
            Approval.ProcessSubmitRequest req1 =  new Approval.ProcessSubmitRequest();
            req1.setComments('Test : Submitting request for approval.');
            req1.setObjectId(c.id);
            req1.setNextApproverIds(new Id[] {UserInfo.getUserId()});
            Approval.ProcessResult result1 = Approval.process(req1);      
            System.assert(result1.isSuccess());
            System.assertEquals('Pending', result1.getInstanceStatus(), 'Instance Status'+result1.getInstanceStatus());
            List<Id> newWorkItemIds = result1.getNewWorkitemIds();
            Approval.ProcessWorkitemRequest req2 = new Approval.ProcessWorkitemRequest();
            req2.setComments('Approving request.');
            req2.setAction('Approve');
            req2.setNextApproverIds(new Id[] {UserInfo.getUserId()});
            req2.setWorkitemId(newWorkItemIds.get(0));
            Approval.ProcessResult result2 =  Approval.process(req2);
            
            vde.isNotApproved = false;
            vde.displayPopUp = false;
            vde.displayApprovalPopUp = true;
            test.stopTest();
      

    }
}

The error is First exception on row 0; first error: REQUIRED_FIELD_MISSING, missing required field: []

at the marked line please help me to resolve this issue.....