Apex class code:
public with sharing class TrackOrderController {
    public string ordernum {get; set;}
    public date orderDate {get; set;}
    public List<Order> Order {get; set;}
    public List<OrderItem> status {get; set;}
    public List<string> vrs {public get; private set;}
    public List<string> pro {public get; private set;} 
    public List<integer> index {public get; private set;}
    
    public PageReference findOrder()
    {
        try{
      
        Order = [SELECT id FROM Order where PoNumber=:ordernum and PoDate =: orderdate ];
        status = [SELECT Product_name__c,Vehicle_Request_Status1__c FROM OrderItem WHERE OrderId =: Order[0].Id];
        system.debug('size-->'+status.size());
        vrs = new List<String>();
        index = new List<integer>();   
        for(integer i=0; i<status.size(); i++){
            index.add(i);
            if(status[i].Vehicle_Request_Status1__c != null){
            vrs.add(status[i].Vehicle_Request_Status1__c);
            }else{
                vrs.add('Null');
            }
        }
           
        system.debug(status);
        system.debug('vrs list--->'+vrs);
        system.debug('index list--->'+index);
        pro = new List<string>();
        for(integer i=0; i<status.size(); i++){
             pro.add(status[i].Product_name__c);
        }

        system.debug('pro list--->'+pro);
        return null;
        }
        catch(Exception ex){ ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.ERROR,'Please check purchase number and date')); return null; }
    }
    public PageReference reset() {
        PageReference newpage = new PageReference(System.currentPageReference().getURL());
    newpage.setRedirect(true);
    return newpage;
    }
}


Test class:
@isTest(SeeAllData=true)
public class TrackOrderControllerTest {
    
static testMethod void findOrder(){
  
      Account acc = New Account();
        acc.name = 'test';
        acc.CR_Number__c = '1234567890';
        acc.CustomerName__c = 'test acc';
        acc.CR_Date_English__c = Date.newInstance(2016, 12, 9);
        acc.CR_Capital__c = 12426;
        acc.Current_Revenue__c = 1233;
        acc.Special_Admin_Rate__c = 123456;
        acc.Security_Type__c = 'ghayth';
        acc.ID_Issuer__c = 'asdasd';
        acc.CR_City__c = 'asdasd';
        acc.Workforce__c = 'sdadad';
        acc.In_Business__c = 'sdasdasdas';
        acc.Nationality_of_Business__c = 'India';
        acc.Arabic_Date__c = Date.newInstance(2016, 10, 7);
        acc.Company_Establishment__c = 'sdads';
        acc.Bank2__c = 'sdfdsf';
        acc.City_Region__c = 'sadf';
        insert acc;  
        
        Product2 newProduct = new Product2();
        newProduct.name = 'abc';
        newProduct.Varient__c = 'asd';
        newProduct.Make__c = 'AMI';
        newProduct.Model__c = 'SEMI TRAILER';
        newProduct.ModelYear__c = 2018;
        newProduct.Fuel_Type__c = 'Petrol';
        newProduct.Transmission__c = 'Powershift';
        newProduct.Internal_Purchase_Price__c = 25;
        newProduct.Registration_Fee__c = 25;
        Insert newProduct;
        
         Pricebook2 customPB = new Pricebook2(Name='Custom Pricebook', isActive=true);
        insert customPB;
        
        PricebookEntry customPrice = new PricebookEntry(
            Pricebook2Id = customPB.Id, Product2Id =newProduct.Id,
            UnitPrice = 12000, IsActive = true);
        insert customPrice;
        
    Order ord = new Order ();
    ord.AccountId =acc.Id;
        ord.PoNumber='PO67543';
        ord.PoDate = Date.newInstance(2016, 10, 5);
        ord.Status ='Draft';
        ord.EffectiveDate= system.today();
        ord.Pricebook2Id = customPB.Id;
    insert ord;
    
    OrderItem orditem = new OrderItem();
    orditem.OrderId = ord.Id;
        Orditem.Vehicle_Request_Status1__c ='PO Approved';
        orditem.PricebookEntryId =customPrice.Id;
        orditem.UnitPrice= 678;
        orditem.Quantity= 7;
    insert orditem;
        
      
    /*  list<OrderItem>status=new List<OrderItem>();
        list<integer>index=new List<integer>();
        status = [SELECT Product_name__c,Vehicle_Request_Status1__c FROM OrderItem WHERE OrderId =: ord.Id];
    for(integer i=0; i<status.size(); i++){
            index.add(i);
        } */
         PageReference testPage = Page.TrackOrder;
         Test.setCurrentPage(testPage);
         testPage.getParameters().put('Id', String.valueOf(ord.Id));
    Test.StartTest(); 
      ApexPages.StandardController sc = new ApexPages.StandardController(ord);
            TrackOrderController  testord = new TrackOrderController();
      testord.findOrder();
      testord.reset ();

    Test.StopTest();
        
  }
}