MY APEX CLASS :

Public class dqtCustomSimple

{
public String dlmstage { get;set;}    

  public dqtCustomSimple()
  
   {
 
   dlmstage = ApexPages.currentPage().getParameters().get('dlmstageid');
      
   }
   Public pagereference redirecttostage()
  
 {
 PageReference newpage= new PageReference('/'+ dlmstage);
      newpage.setRedirect(true);
return newpage;
}

  }

MY TEST CLASS :

@isTest(seeallData = true)
private class dqtCustomSimple_Test
{
    
  static Stage__c stg;
  static Opportunity opp;
   static User U;
   static Engagement_Script__c EP;
    

   
     static testMethod void dqtCustomSimple_Test()
    {
         Test.StartTest();
        CreateData();             
        CreateDQTStage();
       
      
        system.currentpagereference().getparameters().put('id',stg.Id);  
        dqtCustomSimple objdqtCustom = new dqtCustomSimple();
        objdqtCustom.redirecttostage();
       Test.StopTest();
     }
     
     public static void  CreateData()
     {
	 Test.StartTest();
     U = Utils_TestMethods.createStandardUser('alias');  
     insert U;
     System.runAs(U){
     List <PriceBook2> pb2list = new List<PriceBook2>();
     List <Product2> prodlist = new List<Product2>();
     List <PriceBookEntry> pbelist = new List<PriceBookEntry>();
     List <PriceBookEntry> stdPbelist = new List<PriceBookEntry>();
     integer quantity;
      Account acc = Utils_TestMethods.createAccount();
      insert acc;
       acc.ActualUnmanaged__c = true; 
       Database.update(acc);
       system.debug('acc==>'+acc);
     pricebook2 pb2 = [select Id from Pricebook2 where name='Wireline Price Book' and IsActive=true limit 1];
     SFDCtoECSfromTrigger.isttesting = true;  
     opp = Utils_TestMethods.createOpportunity(acc,u);
     insert opp; 
       opp.DLM_Region__c   = 'APAC';
       Database.update(opp); 
       system.debug('opp==>'+opp);
       
      product2 p2= new product2(name='p2test',product_id__c='p2test',isActive=true);
      insert p2;    
      
      pricebookentry pbe = [select Pricebook2Id from pricebookentry where pricebook2id=:pb2.id and product2id =: p2.id limit 1];
    
      Exchange_Rate__c exr=new Exchange_Rate__c(Name='USD',Conversion_Rate__c=10); 
      insert exr;
      Test.StopTest();
      OpportunityLineItem olm=new OpportunityLineItem(Pricebookentryid=pbe.id,Local_Currency__c=exr.id,Local_Booking__c=123455,Opportunityid=opp.id );
      insert olm;
       system.debug('olm==>'+olm);
       
      
      }
    }
    public static void CreateDQTStage()
    {
		 Test.StartTest();

	
        EP = new Engagement_Script__c();
      EP.Engagement_Status__c = 'Open';
      EP.Opportunity__c = opp.Id ;        
      insert EP; 
      system.debug('EP==>'+EP);  
        
     stg = Utils_TestMethods.createStage(opp);
    string strStageName;
    Id rectypeid =[select Id from RecordType where Name=:'Stage 1 RRB'  and SobjectType='Stage__c' limit 1].Id;
    stg.RecordTypeId =rectypeid;
    stg.PCM__c= U.ID;
    stg.Sales__c= U.ID;
    stg.SDA__c = U.ID;                   
    stg.Engagement_Script__c = EP.Id;
    stg.DQT_Approval_Status__c='Approved';    
    insert stg;
       system.debug('stg==>'+stg); 
       
     Stage_Team__c stgTeam = Utils_TestMethods.createStageTeam(stg,U);
     Insert stgTeam; 
	 Test.StopTest();
     stgTeam.User_Role__c = 'Business Operations';
     Database.update(stgTeam);  

        
    }
    
  
    
    
    
}