I have an apex batch class that I was able to get workig in my sandbox enviorment and that is ready for deployment into my production enviroment. 

However when I went to write the test class for this I ran into some trouble, with an error message that says line 50 = Test Class Error: Argument must be an object that implements Database.Batchable.

Can you guys help me get over this hurdle or tell me if i need a new test class code in order to be able to deploy to production? Below are my batch class and my test class thanks. 

Batch Class

global class UpdateContactsVoter implements Database.Batchable<sObject>{
    global Database.QueryLocator start(Database.BatchableContext BC){
        String query = 'Select ID,FirstName,LastName,MailingPostalCode from contact where contact.voter_file_id__c = null';
        return Database.getQueryLocator(query);
    }
    
    global void execute(Database.BatchableContext info, List<contact> scope){
        Set<String> set_Str = new Set<string>();
                                Map<String,Voter_File_TX__c> mp_VoterFile;

        for(Voter_File_TX__c VoterFile : [Select ID,First_Name__c, Last_Name__c,Zipcode__c, Contact__c From Voter_File_TX__c] ){
                                                if(mp_VoterFile==null){
                                                                mp_VoterFile = new Map<String,Voter_File_TX__c>();
                                                }
                                                mp_VoterFile.put(VoterFile.First_Name__c +''+VoterFile.Last_Name__c +''+VoterFile.Zipcode__c,VoterFile);
                                }
                                for(Contact ContactList : scope){
                                                if(mp_VoterFile!=null && mp_VoterFile.containsKey(ContactList.FirstName+''+ ContactList.LastName+''+ ContactList.MailingPostalCode))
            
            {
                                                                mp_VoterFile.get(ContactList.FirstName +''+ ContactList.LastName +''+ ContactList.MailingPostalCode).Contact__c = ContactList.id;
                                                }
                                }
                                if(mp_VoterFile!=null && mp_VoterFile.values()!=null){
                                                update mp_VoterFile.values();
                                }
    }
    
    global void finish(Database.BatchableContext info){
        
    }
}

Test Class
 line 50 = Test Class Error: Argument must be an object that implements Database.Batchable.

@isTest 
public class TestClassUpdateContacts 
{
    static testMethod void testMethod1() 
    {
        List<Contact> lstContact= new List<Contact>();
        List<Voter_File_TX__c> lstVoterfile = new List<Voter_File_TX__c>();
        if(contact.voter_file_id__c == null && voter_file_tx__c.contact__c == null)
        {
        Contact cont = new Contact();
        cont.FirstName ='Test';
        cont.LastName = 'Test';
        cont.id = 'Test';
        cont.MailingPostalCode = 'test';
            
        insert cont;
            
        Voter_File_TX__c vf = new Voter_File_TX__c();
        vf.First_Name__c ='Test';
        vf.Last_Name__c ='Test';
        vf.RNC_ID__c = 'Test';
        vf.Zipcode__c = 'Test'; 
                                vf.First_Name__c = cont.FirstName ;
        vf.Last_Name__c = cont.LastName ;
        vf.Zipcode__c = cont.MailingPostalCode ;
        vf.Contact__c = cont.Id ;
        
        insert vf;
       
        cont.FirstName = vf.First_Name__c ;
        cont.LastName = vf.Last_Name__c ;
        cont.MailingPostalCode = vf.Zipcode__c;
        cont.RNC_ID__c = vf.RNC_ID__c ;
            
                                update cont;
        }
        else {
         contact cont1 = new Contact(); 
         Voter_File_TX__c vf1 = new Voter_File_TX__c();
         cont1.Voter_File_ID__c = null;
         vf1.Contact__c = null; 
          
        }
        insert lstContact;
        update lstContact;
        
        Test.startTest();

            TestClassUpdateContacts obj = new TestClassUpdateContacts();
            DataBase.executeBatch(obj); 
            
        Test.stopTest();
    }
}