Methods defined as TestMethod do not support Web service callouts error

Question

This is my controller class.

public with sharing class RSLeadReportcontroller {

    public List<RSLeadReport> ConsoleWrapperList{get;set;}
    
    public List<RSLeadReport> getperformcallout(){
    
        ConsoleWrapperList = new List<RSLeadReport>();
        
        HttpRequest req = new HttpRequest();
        HttpResponse res = new HttpResponse();
        Http http = new Http();
        req.setTimeout(60000);
        
        String authorization= String.valueOf([SELECT Authentication__c FROM RS_External_Endpoint__mdt WHERE DeveloperName = 'RS_Token' LIMIT 1].Authentication__c);   
        
        req.setHeader('Authorization', 'Bearer '+authorization);
        req.setHeader('Content-Type', 'application/json');
        req.setEndpoint('https://rsdv-dt-loc-na-api.exxonmobil.com/api/v2/search/get/leads');
        req.setMethod('GET');
        
        res = http.send(req);
        
        if(res.getstatusCode() == 200 && res.getbody() != null){
        
            ConsoleWrapperList=(List<RSLeadReport>)json.deserialize(res.getbody(),List<RSLeadReport>.class);
        
        }
            
        return consolewrapperlist;
   }
        
    public PageReference exportToExcel(){
        PageReference retURLExcel = new PageReference('/apex/WebApp_Leads_excel');
        return retURLExcel;
    } 
          
}

And this is my test class.

@isTest
public class Test_RSLeadReportcontroller{
 
  @testSetup
  public static void setupTestData(){
    Test.startTest();
    Lead lead_Obj = new Lead(LastName = 'LastName885', FirstName = 'First641', MiddleName = 'Middl705', Company = 'Company493', Street = 'PratapNagar', City = 'Miami', State = 'Florida', PostalCode = '302022', Country = 'USA', MobilePhone = '54343-63122', Email = 'Email28@test.com', Website = 'http://test29.com', Status = 'New', Webapp_Lead_ID__c = 'Webap415', Lead_Pardot__c = false);
    Insert lead_Obj; 
    Test.stopTest();
  }
  
  public class RSCallout implements HttpCalloutMock{

            public HTTPResponse respond(HTTPRequest request) {
                // Create a fake response
                HttpResponse response = new HttpResponse();
                response.setHeader('Content-Type', 'application/json');
                response.setBody('{"data": {"identity": {"accountGroup": {"code": "0001"},"salesforceId": "0014100001eCl2U", "tradingName": "CPAC ROOF TILE" }}}');
                response.setStatusCode(200);
                //response.setStatus('Customer Found');
                return response;
            }        
  } 

  public static testMethod void test_exportToExcel_UseCase1(){
    List<Lead> lead_Obj  =  [SELECT LastName,FirstName,MiddleName,Company,Street,City,State,PostalCode,Country,MobilePhone,Email,Website,Status,Webapp_Lead_ID__c from Lead];
    System.assertEquals(true,lead_Obj.size()>0);
    RSLeadReportcontroller obj01 = new RSLeadReportcontroller();
    obj01.ConsoleWrapperList = new List<RSLeadReport>();
    obj01.exportToExcel();
  }

  public static testMethod void test_getperformcallout_UseCase1(){
    Test.startTest();
    List<Lead> lead_Obj  =  [SELECT LastName,FirstName,MiddleName,Company,Street,City,State,PostalCode,Country,MobilePhone,Email,Website,Status,Webapp_Lead_ID__c from Lead];
    System.assertEquals(true,lead_Obj.size()>0);
    
    RSLeadReportcontroller obj01 = new RSLeadReportcontroller();
    obj01.ConsoleWrapperList = new List<RSLeadReport>();
    obj01.getperformcallout();
    Test.setMock(HttpCalloutMock.class, new RSCallout());
    Test.stopTest();  
  }
             
}

Answer 1

You need to call Test.setMock() prior to running the code that is trying to make the callout, not afterwords.

Calling that method is what causes Salesforce to substitute the real callout for the mock one that you're providing (when the callout is attempted).