Test class for RequestData class [duplicate]

Question

  @HttpPost
    global static List<HHSurvey> getHHSurveyList() {

    RestRequest req = RestContext.request;
    RequestData  mRequestData = (RequestData)JSON.deserialize(req.requestBody.toString(),RequestData.class);
    List<HH_Survey__c> hhSList = new List<HH_Survey__c>();
    Map<String,List<HH_Housing__c>>hhHList=new Map<String,List<HH_Housing__c>>();
    List<HHSurvey> hhSurveyList = new List<HHSurvey>();
    Set<String> hhSurveyIds=new Set<String>();
    DateTime FromDate=null;
    DateTime ToDate=null;


    if(mRequestData!=null&& mRequestData.AgentMobileNo!=null&&mRequestData.AgentMobileNo!=''
       &&mRequestData.FromDate!=null&&mRequestData.FromDate!='0'&&mRequestData.ToDate!=null&&mRequestData.ToDate!='0')
    {

    FromDate=datetime.newinstance(long.valueOf(mRequestData.FromDate));
    ToDate=datetime.newinstance(long.valueOf(mRequestData.ToDate));



    if(mRequestData.FromDate.equals(mRequestData.ToDate))
    {

      **hhSList** = [SELECT Id,Family_s_monthly_income__c,Do_you_have_your_own_house__c,Saral_Jeevan_channel_is_accessible__c,Need_Remedy_Help1__c,Irrigated_land_In_Acre__c,AgentMobileNo__c,Main_occupation_of_the_family__c,Household_Serial_Number__c,Consent_Status__c,Hamlet_Segment_Camp__c from HH_Survey__c where AgentMobileNo__c=:mRequestData.AgentMobileNo AND AgentMobileNo__c<>null And CreatedDateWithNoTime__c<> null
               AND CreatedDateWithNoTime__c=: FromDate.Date() order by CreatedDateWithNoTime__c Desc ];

    }
    else
    {

     hhSList = [SELECT Id,Family_s_monthly_income__c,Do_you_have_your_own_house__c,Saral_Jeevan_channel_is_accessible__c,Dry_land_In_Acre__c,Mobile1__c,Loan_Amount__c,Respondent_Name__c,Landmark__c from HH_Survey__c where AgentMobileNo__c=:mRequestData.AgentMobileNo AND AgentMobileNo__c<>null And CreatedDateWithNoTime__c<> null
               AND CreatedDateWithNoTime__c>=: FromDate.Date() AND CreatedDateWithNoTime__c<=:ToDate.Date()   order by CreatedDateWithNoTime__c Desc ]; 

    }

     if(hhSList !=null&&hhSList.size()>0 )
    {

     for(HH_Survey__c hhSurvey :hhSList ){

      hhSurveyIds.add(hhSurvey.Id);

     }

     hhHList=getHousingList(hhSurveyIds);

     for(HH_Survey__c hhs : hhSList ){
         HHSurvey hs = new HHSurvey();
         hs.Id = hhs.Id;
         hs.FamilyMonthlyIncome= hhs.Family_s_monthly_income__c;
         hs.Doyouhaveyourownhouse= hhs.Do_you_have_your_own_house__c;
         hs.SaralJeevanChannelAccess= 
         hhs.Saral_Jeevan_channel_is_accessible__c;
         hs.Remarks= hhs.Remarks__c;
         hs.TV= hhs.Do_you_have_TV_in_your_house__c ;
         hs.SurveyNo= hhs.HH_Survey_Id__c;


         List<HHHouse> setHH=null;
         if(hhHList!=null &&hhHList.size()>0 &&hhHList.containsKey(hs.Id)){
          setHH=setHousingList(hhHList.get(hs.Id));
          hs.HouseList.addAll(setHH);
         }
        hhSurveyList.add(hs);

      }

   }

      return hhSurveyList ;

    }


global class HHHouse{
  String Id;
  String HHSurveyId;
  Decimal ApproxSize;
  Decimal HouseType;
  Decimal HouseAge;  
}


global class RequestData{

  String AgentMobileNo;
  String FromDate;
  String ToDate;       

}

    global class HHSurvey{
    String Id;
    Decimal FamilyMonthlyIncome;
    String Doyouhaveyourownhouse;
    String SaralJeevanChannelAccess;
    String Remarks;
    String Village;
    Decimal DryLandInAcre;
    String MobileOne;
    Decimal Houshold;
    Decimal BalanceLoanAmountOutstanding;
    Decimal TotalLandHoldingAcre;
    Decimal SolutionDate;
    Decimal DOBOfFamilyHead;
    String NameofHouseholdHead;
    Decimal SurveyDate;
    String HSC;
    String ConsentStatus;
   List<HHHouse> HouseList=new List<HHHouse>();

   }

Test class

static testMethod void SurveylistTest()              
   {     
    Test.startTest();
    JSONGenerator gen = JSON.createGenerator(true);

    gen.writeStartObject();
    gen.writeStringField('AgentMobileNo', '7022834238');  
    gen.writeStringField('FromDate', '1527964200000');  
    gen.writeStringField('ToDate', '1527964200000');  
    gen.writeEndObject();

    String json =gen.getAsString();

    RestRequest req = new RestRequest(); 
    RestResponse res = new RestResponse();

    req.requestURI = 'https://cs5.salesforce.com/services/apexrest/getHHSurveyList/';  
    req.httpMethod = 'POST';
    req.requestBody= blob.valueOf(json);
    RestContext.request = req;
    RestContext.response = res;        


    List<WS_GetHHSurveyList.HHSurvey> surveylist = WS_GetHHSurveyList.getHHSurveyList();
    System.assert(surveylist.size() ==0);

    Test.StopTest();  
   }