here is my class


global class BT_Invoicing_New_Override_Crtl {

    public ApexPages.StandardController stdCon;
    public BT_Invoicing__c btinvoice{get;set;}
    public Static Integer BtjoblstSize;
    public Double Local_DFE_Quantity;
    public Double Local_Invoice_Cost_excl_vat;
    public String recordId;
    BT_Invoicing__c btinvoiceRecord;
    Public Static String btEstimateNumber;

    public BT_Invoicing_New_Override_Crtl(ApexPages.StandardController controller) 
    {
        stdCon= controller;
        btinvoice= (BT_Invoicing__c)stdCon.getRecord();
        recordId=ApexPages.currentPage().getParameters().get('id');
    } 
   
    public PageReference Save(){
    try{

        btinvoiceRecord= (BT_Invoicing__c)stdCon.getRecord();
       
        
            if(btinvoiceRecord.Invoice_Cost_excl_vat__c==null)
            Local_Invoice_Cost_excl_vat=0;
         else
            Local_Invoice_Cost_excl_vat=btinvoiceRecord.Invoice_Cost_excl_vat__c;
            
          if(btinvoiceRecord.DFE_Quantity__c==null)
             Local_DFE_Quantity=0;
          else
              Local_DFE_Quantity=btinvoiceRecord.DFE_Quantity__c;
            
     if(btinvoiceRecord.Pay__c=='Yes'&& ( Local_Invoice_Cost_excl_vat- Local_DFE_Quantity > 0)
                                         && btinvoiceRecord.Reject_Invoice__c==false && btinvoiceRecord.Invoice_In_Query__c==false)
          btinvoiceRecord.Invoice_Status__c='PAID-DFE';
     else if(btinvoiceRecord.Pay__c=='Yes'&& (Local_Invoice_Cost_excl_vat- Local_DFE_Quantity==0) 
                                         && btinvoiceRecord.Reject_Invoice__c==false && btinvoiceRecord.Invoice_In_Query__c==false)
          btinvoiceRecord.Invoice_Status__c='Paid';
     else if(btinvoiceRecord.Pay__c=='No' && btinvoiceRecord.Reject_Invoice__c==false && btinvoiceRecord.Invoice_In_Query__c==false)
          btinvoiceRecord.Invoice_Status__c='Active';
        
     
        
        upsert btinvoicerecord;
                
        PageReference pageref = new Pagereference('/'+btinvoicerecord.id);
        pageref.setRedirect(true);
        return pageref;
        
        return null;
      }
    catch(Exception ex){
        ApexPages.Message msg = new ApexPages.Message(ApexPages.Severity.ERROR,ex.getDMLMessage(0));
        ApexPages.addMessage(msg);
        return null;
    }    
  }
  
  public PageReference SaveandNew(){
    try{
        stdCon.Save();  
        return new PageReference('/'+stdCon.getRecord().getSObjectType().getDescribe().getKeyPrefix()+'/e?');
         
      }
    catch(Exception ex){
        ApexPages.Message msg = new ApexPages.Message(ApexPages.Severity.ERROR,ex.getDMLMessage(0));
        ApexPages.addMessage(msg);
        return null;
    }    
  
  }
  
  @RemoteAction
 Public Static Integer GetEstimateListsize(String btestimateno)
  {
         List<BT_Job__c> Btjoblst=[Select Id,Name,Estimate_No__c From BT_Job__c Where  Estimate_No__c=:btestimateno];
         BtjoblstSize=Btjoblst.size();
         System.debug('BtjoblstSize='+BtjoblstSize);
         return BtjoblstSize;
  }
  
   
}

n this is my test class

@istest
public class BT_Invoicing_New_Override_Crtl_Test {
    
     public static testmethod void myTestUnit1(){
      PageReference pageRef = Page.BT_Invoicing_New_Override;
        Test.setCurrentPage(pageRef);
        
        BT_Invoicing__c btInvObj = new BT_Invoicing__c();
        btInvObj.Invoice_Cost_excl_vat__c=55.20;
        btInvObj.DFE_Quantity__c=45.30;
        btInvObj.Pay__c='Yes';
        btInvObj.Reject_Invoice__c=false;
        btInvObj.Invoice_In_Query__c=false;
        
        insert btInvObj;
         
          ApexPages.StandardController sc = new ApexPages.standardController(btInvObj);
       BT_Invoicing_New_Override_Crtl sic = new  BT_Invoicing_New_Override_Crtl(sc);
      sic.Save(); 
     } 
     public static testmethod void myTestUnit2(){
      PageReference pageRef = Page.BT_Invoicing_New_Override;
        Test.setCurrentPage(pageRef);
        
        BT_Invoicing__c btInvObj = new BT_Invoicing__c();
        btInvObj.Invoice_Cost_excl_vat__c=45.30;
        btInvObj.DFE_Quantity__c=45.30;
        btInvObj.Pay__c='Yes';
        btInvObj.Reject_Invoice__c=false;
        btInvObj.Invoice_In_Query__c=false;
        insert btInvObj;
         
         
     
         ApexPages.StandardController sc = new ApexPages.standardController(btInvObj);
       BT_Invoicing_New_Override_Crtl sic = new  BT_Invoicing_New_Override_Crtl(sc);
      sic.Save(); 
     } 
     public static testmethod void myTestUnit3(){
      PageReference pageRef = Page.BT_Invoicing_New_Override;
        Test.setCurrentPage(pageRef);
        
        BT_Invoicing__c btInvObj = new BT_Invoicing__c();
        btInvObj.Invoice_Cost_excl_vat__c=00.00;
        btInvObj.DFE_Quantity__c=00.00;
        btInvObj.Pay__c='No';
        btInvObj.Reject_Invoice__c=false;
        btInvObj.Invoice_In_Query__c=false;
        insert btInvObj;
         
         
    
         ApexPages.StandardController sc = new ApexPages.standardController(btInvObj);
       BT_Invoicing_New_Override_Crtl sic = new  BT_Invoicing_New_Override_Crtl(sc);
      sic.Save(); 
     } 
    public static testmethod void myTestUnit4(){
      
       
        BT_Invoicing__c btInvObj = new BT_Invoicing__c();
        btInvObj.Invoice_Cost_excl_vat__c=10.00;
        btInvObj.DFE_Quantity__c=10.00;
        btInvObj.Pay__c='No';
        btInvObj.Reject_Invoice__c=false;
        btInvObj.Invoice_In_Query__c=false;
        insert btInvObj;
       BT_Invoicing__c btInvObj1=[select id , Invoice_Status__c from  BT_Invoicing__c where id=:btInvObj.id];
       
        PageReference pageRef = Page.BT_Invoicing_New_Override;
        Test.setCurrentPage(pageRef);
        Test.startTest();
      
      ApexPages.StandardController sc = new ApexPages.standardController(btInvObj1);
       BT_Invoicing_New_Override_Crtl sic = new  BT_Invoicing_New_Override_Crtl(sc);
      sic.SaveandNew();
      
        

       }
}

I need to increase the code coverage ,its nt covering remote action method and catch block
please help me out