global class deleteFireScoreSummaryRecords implements Database.batchable<FIRE_Score_Summary__c>,schedulable
{ 
   global Iterable<FIRE_Score_Summary__c> start(Database.BatchableContext BC)
   {
       FIRE_Score_Configuration__c defaultFireScoreConfiguration = FIRE_Score_Configuration__c.getValues('Default');
       if(defaultFireScoreConfiguration!=null && defaultFireScoreConfiguration.No_Of_Days_Historical_Data_to_Keep__c!=null)
       {
           DateTime dt=System.now().addDays(Integer.Valueof(-1*defaultFireScoreConfiguration.No_Of_Days_Historical_Data_to_Keep__c));
           
           return [SELECT Id,Name from FIRE_Score_Summary__c where Scoring_Date_and_Time__c<=:dt Limit 20];
       }
       else
       {
            return [SELECT Id,Name from FIRE_Score_Summary__c];
       }
   }
   global void execute(Database.batchableContext info, List<FIRE_Score_Summary__c> scope)
   {
       if(scope!=null && scope.size()>0)
       {   
           delete scope;
       }     
   }
   global void finish(Database.batchableContext info)
   {     
   }
   global void execute(SchedulableContext sc){
        deleteFireScoreSummaryRecords thisBatch = new deleteFireScoreSummaryRecords();
        Database.executebatch(thisBatch,1);
    } 
}
=====================================================>
my test class
@isTest
public class deleteFireScoreSummaryRecordsTest {

    @isTest
    public static void testMethod1(){
       FIRE_Score_Configuration__c  defaultFireScoreConfiguration = new FIRE_Score_Configuration__c();
       defaultFireScoreConfiguration.Enable_FIRE_Score__c = TRUE;
       defaultFireScoreConfiguration.Account_Record_Types_to_Include_for_FIRE__c = 'Both';
       defaultFireScoreConfiguration.Include_Active_Accounts_Only__c = TRUE;
       defaultFireScoreConfiguration.Running_Date__c = 'CURRENT' ;
       defaultFireScoreConfiguration.Name = 'Default';
       defaultFireScoreConfiguration.Allow_Single_Account_Calculation__c= TRUE;
       defaultFireScoreConfiguration.Number_of_Weeks_to_Process_Data__c=2;
       defaultFireScoreConfiguration.No_Of_Days_Historical_Data_to_Keep__c=2;
       insert defaultFireScoreConfiguration;
        System.debug (' defaultFireScoreConfiguration ====> '+ defaultFireScoreConfiguration);
        
        Id systemAdminProfileId = [SELECT Id FROM Profile WHERE Name = 'System Administrator' LIMIT 1].Id;

        User userExample = new User();
        userExample.Username = 'emailtst@test.com';
        userExample.FirstName = 'First';
        userExample.LastName = 'Last';
        userExample.Alias = 'Alias';
        userExample.Email = 'emailtest@test.com';
        userExample.TimeZoneSidKey = 'America/New_York';
        userExample.LocaleSidKey = 'en_US';
        userExample.EmailEncodingKey = 'ISO-8859-1';
        userExample.ProfileId = systemAdminProfileId;
        userExample.LanguageLocaleKey = 'en_US';
        insert userExample;
        
        Account account = new Account(Account_Type__c='Sub Agent',Name = 'Test Account',status__c='Active' , CSM__c=userExample.id , SSD__c=userExample.id , BDR__c=userExample.id , Coverage__c= 'Strategic' , Sales_Engineer__c=userExample.id);  
        insert account; 
          
         List<FIRE_Score_Summary__c> fireScoreSummaryList = new List<FIRE_Score_Summary__c>();
           for( Integer i=0 ; i<=2 ; i++){
                FIRE_Score_Summary__c fireHeaderRec = new FIRE_Score_Summary__c();
                fireHeaderRec.Account__c=account.Id;
                fireHeaderRec.Scoring_Date_and_Time__c=System.now();
                fireScoreSummaryList.add(fireHeaderRec);
        }
            insert fireScoreSummaryList;
      
        deleteFireScoreSummaryRecords testFire = new deleteFireScoreSummaryRecords();
        Database.executeBatch(new deleteFireScoreSummaryRecords(),10);
        testFire.execute(null);
        testFire.execute(null, fireScoreSummaryList);
    }    
}