Writing test class for wrapper class to simulate the business process

Question

I am trying to write a test class for a Wrapper class. The wrapper class pulls one objects to make it as a checkbox list.

Could anyone help me to adjust the code I wrote below? I have written test classes before but have never tried with wrapper class

Controller;

/**
 * In addition, this class provides methods for displaying sObject Location__c
 * as a selectoption in checkboxes and latter to be included as an insert

 * @author:  Adnan Zahry
 * @Last Update: 05/08/2019
 */


public class desiredLocationsWrapper{

    //this variable handles location list for which appear on visualforce as checkbox option
    public List<wrapperLocationCheckbox> LstWrp{get;set;}

    //this variable handles selected location and stored back into controller
    public List<wrapperLocationCheckbox> LstWrp_Selected;

    private Id TleadId;


    //constructor
    public desiredLocationsWrapper(){
        LstWrp = new List<wrapperLocationCheckbox>();       
        TleadId = ApexPages.currentPage().getParameters().get('what_id');

        String s; 
        try{
            s = [SELECT Country__c from TLead__c where Country__c != null and Id = :TleadId ].Country__c;
        }
        catch(Exception ex){
            Apexpages.addMessage(new ApexPages.Message(ApexPages.SEVERITY.FATAL, 'TLead record does not have any country associated with'));
        }

        List<Location__c> locList = new List<Location__c>([SELECT City__c, Id, Region__c FROM Location__c where Country__c = :s ORDER BY City__c asc]);

        for(Integer i=0; i<locList.size(); i++){
            LstWrp.add(new wrapperLocationCheckbox(locList[i]));
        }
    }

//--------------------------------------------------------------
    //define the class for which we want to use the checkbox
        public class wrapperLocationCheckbox{

            public boolean checkbox{get;set;}
            public Location__c loc{get;set;}

        /*//Constructor with no arg
        public wrapperLocationCheckbox(){

        }

        //Constructor with parameter
        public wrapperLocationCheckbox(boolean c, String S, Location__c l){

            this.checkbox=c;
            this.SLNo=s;
            this.loc=l;
        }
        */

        //Another constructor with parameter
        public wrapperLocationCheckbox(Location__c l){

            this.loc=l;
            checkbox=false;
        }
    } 
//---------------------------------------------------------------
        public PageReference save(){

        List<Location__c> existingLocations = new List<Location__c>();
        LstWrp_Selected = new List<wrapperLocationCheckbox>();
        //iterate LstWrp collection and pass the values back into controller and assing them to LstWrp_Selected
        for(wrapperLocationCheckbox wrp : LstWrp){

            if(wrp.checkbox==true){
                LstWrp_Selected.add(wrp);           
        }
      }

        //Iterate LstWrp_Selected 
        for(wrapperLocationCheckbox wrp1 : LstWrp_Selected){ 

            DesiredLocation__c dloc = new DesiredLocation__c();

            /// for the new selected location, get the id from the object
            existingLocations = [SELECT Id, Name from Location__c WHERE Name =: wrp1.loc.City__c];

            if(!existingLocations.isEmpty()){
                dloc.TLead__c = ApexPages.currentPage().getParameters().get('what_id');
                dloc.Area__c = wrp1.loc.Id;
                dloc.Name = dloc.TLead__c + ' - ' + dloc.Area__c;
                insert dloc;

           }
        }

            PageReference pr = new PageReference('/'+ApexPages.currentPage().getParameters().get('what_id'));
                return pr;
    }
//---------------------------------------------------------------
    public PageReference cancel(){
        PageReference pr = new PageReference('/'+ApexPages.currentPage().getParameters().get('what_id'));
        pr.setRedirect(true);

        return pr;
    }

//---------------------------------------------------------------
    //Return TLead list in search result form
            /*String keyword;
            List<TLead__c> tleadlist;

            public String getkeyword(){
                return keyword;
            }

            public void setkeyword(String s){
                keyword = s;
            }

            public List<TLead__c> gettleadlist(){
                return tleadlist;
            }

            public PageReference showResults(){
                List<List<TLead__c>> searchList = [FIND :keyword RETURNING TLead__c(Name, Id)] ;
                tleadList = (TLead__c[])searchList[0];
                PageReference pr = new PageReference('/apex/incDLocationsTleadLookup');
                pr.setRedirect(false);
                return pr;
            }*/            
//--------------------------------------------------------------------
}

Below is My approach in test class, I get only 59% coverage and some parts are confusing to me;

@isTest(SeeAllData=true) 
public class desiredLocationsWrapperTest {
    public static desiredLocationsWrapper instance = new desiredLocationsWrapper();

    @isTest(SeeAllData=true) 
    public static void dlocWrapper(){
        Tlead__c tl = new Tlead__c(
          Name = 'Test Adnan1',
          Country__c = 'ID',
          Lead_Source__c = 'Facebook Lead Ad',
          Mobile__c = '81380577103');
        insert tl;

        Location__c lc = new Location__c(
          Name = 'Ciomas',
          Country__c = 'ID',
          City__c = 'Bogor',
          Region__c = 'Jawa Barat');
        insert lc;
    }
    @isTest(SeeAllData=true) 
    public static void saveTest(){

        DesiredLocation__c dloc1 = new DesiredLocation__c(Name = 'daw', Area__c = 'a0H0D0000034IMx', Tlead__c = 'a030D000003LUyh' );
        insert dloc1;
        instance.save();
    }
    @isTest
    public static void cancelTC01(){
        instance.cancel();
    }
}

Answer 1

Add below things to your test methods

You need to set the current page for the test.

PageReference myVfPage = Page.YourPageName;
Test.setCurrentPage(myVfPage);

Then you need to add the URL parameter like below. First, query the country record and pass its value

ApexPages.currentPage().getParameters().put('what_id',countryObj.Id);

Always try to avoid (SeeAllData=true), you delete it keeping @isTest only as it's not required. The reason you can find here.

Also, it's advised to go through the apex testing documentation.