populate values in a wrapper class variable which is a list<wrapperclass>

Question

    responseSize = ParsedResponse.results.size();
    if(tResults.keySet().size()>0){                      
    for(Results re : ParsedResponse.results){            
       customObj tLocs = new customObj(Building_Name__c=re.buildingname,                                                                                  
                                       Street_Name__c = re.streetName,                                            
                                       country__c = re.country,                                                                                 
                                       state__c = re.state,                                                 
                                       city__c = re.city,                                                                                  
                                       Zip_Code__c = re.postal,                                                
                                       external_id__c = re.externalkey                                                                              
       );
               
    public class GetResponseBodyClass {       
            public List<Results> results;
    } 
    
    public class Results {
            public String street;
            public String country;
            public String state;
            public String city;
            public String postal;
    }    

Below is the test class-

    @isTest
    private class apiSync_Test{
        
        @isTest
        private static void insertTls(){
            apiSync.GetResponseBodyClass tl = new apiSync.GetResponseBodyClass();        
            HttpResponse resp = new HttpResponse();
            resp.setHeader('Content-Type', 'application/json');  
            resp.setStatusCode(200);
            resp.setBody(apiSync_Test.getResponse());  
            QueueHttpMock mock = new QueueHttpMock();
            mock.addResponse(resp);
            Test.setMock(HttpCalloutMock.class,mock);        
        }
        
        public static string getResponse()
        {
            apiSync.GetResponseBodyClass rbc = new apiSync.GetResponseBodyClass();
            rbc.total = 500;
            rbc.page = 1;   
           // rbc.results = ({buildingname='TEST';street='ONE';uniqueKey='65776'},{buildingname='TEST';street='TWO';uniqueKey='57767'});
            return JSON.serialize(rbc);
        }      
        
    }

Answer 1

Just create a list of wrapper with your dummy data as shown below

List<apiSync.Results> results = new List<apiSync.Results>();

apiSync.Results res1 = new apiSync.Results();
res1.buildingname = 'test';
res1.street = 'test';
...
results.add(res1);

/* repeat for multiple result entries */

...
rbc.results = results;
return JSON.serialize(rbc);