Hi Ispita_Navatar, I will give you the full code as I think I have covered you suggustion elsewhere,

** My controller extension **

public class AnnRevCon2edit {

    public String patid { get; set; }
   
    public String conid { get; set; }

    public final INS_Annual_Review__c ar;
  
    ApexPages.StandardController stdCtrl;
   
    public AnnRevCon2edit(ApexPages.StandardController stdController) {
        stdCtrl=stdController;
        this.ar = (INS_Annual_Review__c)stdController.getRecord(); // gets single records from this page.
        ar.ClientID__c = ApexPages.currentPage().getParameters().get('cid'); // assign's cid to ClientID__c
    }
  
    // puts Client info on screen **** working!
    public String Id  { get; private set; } 
 
    // temporary initialisation of contact controller to allow call to info held there.
    public ApexPages.StandardSetController setCon {
        get {
            if(setCon == null) {
                patid = ApexPages.currentPage().getParameters().get('cid'); // loads cid value into patid
                    if(ApexPages.currentPage().getParameters().get('cid')!= null){     
                        conid = '?cid='+ApexPages.currentPage().getParameters().get('cid');
                    }
                Id id = ApexPages.currentPage().getParameters().get('cid');
                setCon = new ApexPages.StandardSetController(Database.getQueryLocator(              
                      [select name, Client_DOB__c, Contact_Ref__c, DNR_Authorisation_Uploaded__c from Contact where Id = :id]));
            }
            return setCon;
        }
        set;
    }

    // Initialize setCon and return a list of records
   
    public List<Contact> getContacts() {
         return (List<Contact>) setCon.getRecords();
    }
    // puts Client info on screen **** working

    //extending the save
      public PageReference saveandnotes() {
          stdCtrl.save(); // This takes care of the details for you.
          PageReference pr = Page.PN;
          pr.getParameters().put('cid',ApexPages.currentPage().getParameters().get('cid'));
          pr.getParameters().put('form','Annual_Review2__c');
          pr.setRedirect(true);
        return pr;
    } 
             
}

**My full test code **

@isTest
private class AnnRevCon2editTest
{
        static PageReference pageRef;
        static String isString {get; set; }
   
    Public static TestMethod void AnnRevCon2editTest()
        {
            pageRef = new PageReference('Annual_Review2e'); // used to set a page         
            test.setCurrentPage(pageRef);  // set starting page
            ApexPages.CurrentPage().getParameters().put('cid', '003R000000Y7Gw4');
                       
            // this builds the constructor for the controller which links this to the correct object
            INS_Annual_Review__c testrev = new INS_Annual_Review__c(ClientID__c = '003R000000Y7Gw4',
                Any_Other_info__c = 'djshfgjdh',Communication__c = 'abc',Sup_Net__c = 'sgdsfg',Functional__c = 'Yes',
                Falls__c = True,Past_History__c = 'sdfgksjf',PC_ra__c = True,OT__c = True,
                Med_Dose__c = 'vcxv',invOther__c = False,Med_Frequency__c = 'ageragearg',
                GTS__c = False, Med_Name__c = 'dgfgdfg');
                Insert testrev;

            ApexPages.StandardController stdController = new ApexPages.StandardController(testrev);
            AnnRevCon2edit AR = new AnnRevCon2edit(stdcontroller);
           
            List<INS_Annual_Review__c> Reviews = new List<INS_Annual_Review__c>{};
            for (Integer i = 0; i < 10; i++) {
                INS_Annual_Review__c revs = new INS_Annual_Review__c(ClientID__c = '003R000000Y7Gw4',
                Any_Other_info__c = 'djshfgjdh' + i,Communication__c = 'abc' + i,Sup_Net__c = 'sgdsfg' + i,Functional__c = 'Yes' + i,
                Falls__c = True,Past_History__c = 'sdfgksjf' + i,PC_ra__c = True,OT__c = True,
                Med_Dose__c = 'vcxv' + i,invOther__c = False,Med_Frequency__c = 'ageragearg' + i,
                GTS__c = False, Med_Name__c = 'dgfgdfg' + i);
                Reviews.add(revs);
                }
            System.debug('Inserting contact detail(single record validation)');
                test.StartTest();
                    insert Reviews;
                test.StopTest();
            System.assertEquals(Reviews.size()>5, true);
          
        }
       
       // checks contacts exist ans displays the right one on screen.
    Public static TestMethod void getSetCon()
        {
            pageRef = new PageReference('Annual_Review2e'); // used to set a page         
            test.setCurrentPage(pageRef);  // set starting page
            ApexPages.CurrentPage().getParameters().put('cid', '003R000000Y7Gw4');
     
         // this builds the constructor for the controller which links this to the correct object
            INS_Annual_Review__c testrev = new INS_Annual_Review__c(ClientID__c = '003R000000Y7Gw4',
                Communication__c = 'abc',Functional__c = 'Yes',PC_ra__c = True,OT__c = True,
                Med_Dose__c = 'vcxv',invOther__c = False,Med_Frequency__c = 'ageragearg',
                GTS__c = False, Med_Name__c = 'dgfgdfg');
                Insert testrev;

            ApexPages.StandardController stdController = new ApexPages.StandardController(testrev);
            AnnRevCon2edit AR = new AnnRevCon2edit(stdcontroller);
     
        // Create some test data 
        List<Contact> contacts = new List<Contact>{};
        for (Integer i = 0; i < 10; i++) {
            Contact c = new Contact(Is_Client__c = True, LastName = 'notlob' +i, Client_Address_1__c = 'Address'+i,
            Client_County__c = 'somecounty' +i, ContactType__c = 'Client' + i, Client_Town__c = 'Bolton' + i, Client_Postcode__c = 'postcode' + i,
            Client_DOB__c = System.today());
            contacts.add(c);
        }
    
        // Insert the test data - it will not be committed to the database,
        // since this is a test method
        insert contacts;
    
        System.assertEquals(contacts.size()>5, true);
     
        List<contact> the_contacts = AR.getContacts();
            system.assert(the_contacts.size()>0);
        }

        Public Static TestMethod void saveandnotes()
        {
            pageRef = new PageReference('Annual_Review2e'); // used to set a page         
            test.setCurrentPage(pageRef);  // set starting page
            ApexPages.CurrentPage().getParameters().put('cid', '003R000000Y7Gw4');
            ApexPages.CurrentPage().getParameters().put('form', 'INS_Annual_Review__c');
                       
            // this builds the constructor for the controller which links this to the correct object
            INS_Annual_Review__c testrev = new INS_Annual_Review__c(ClientID__c = '003R000000Y7Gw4',
                Communication__c = 'abc',Functional__c = 'Yes',PC_ra__c = True,OT__c = True,
                Med_Dose__c = 'vcxv',invOther__c = False,Med_Frequency__c = 'ageragearg',
                GTS__c = False, Med_Name__c = 'dgfgdfg');
                Insert testrev;

            ApexPages.StandardController stdController = new ApexPages.StandardController(testrev);
            AnnRevCon2edit AR = new AnnRevCon2edit(stdcontroller);
          
           // String nextPage = controller.saveandnotes().getUrl();

            //system.assertEquals('/apex/PN?cid=003R000000Y7Gw4', nextPage);

        }
}

The lines in red just throw an error when left in.

Thanks Steve