Batch class with test to update all accounts in the org. Uses database.getquerylocator();

batchclass1.cls

global class batchclass1 implements Database.Batchable<sobject>,Database.Stateful {
	global integer count = 0;
	
	global Database.QueryLocator start(Database.BatchableContext bc) {
		return Database.getQueryLocator('select id,name from account');
	}
	
	global void execute(Database.BatchableContext bc,List<account> acc_lst) {
		List<account> acc_update_lst = new List<account>();
		for(account a: acc_lst) {
			a.name+=1;
			acc_update_lst.add(a);
			count+=1;
		}
		update acc_update_lst;
	}
	
	global void finish(Database.BatchableContext bc) {
		system.debug('Accounts updated = '+count);
		system.debug('batch job id = '+bc.getJobId());
	}
	
}

batchclass1_test.cls

@isTest(SeeAllData=true)
public class batchclass1_test {
    
    @isTest
    public static void testit() {
        Test.startTest();
        batchclass1 abc = new batchclass1();
        Id batchId = Database.executeBatch(abc);
        system.debug('batchId = ' + batchId);
        Test.stopTest();
    }

}