@isTest
public class CaseStatusChangeBatchTester {

    static testMethod void CaseStatusChangeBatchUnitTest() {

        Account testAcc = new Account();
        testAcc.Name = 'Test Account';
        insert testAcc;

        Contact cont = new Contact(AccountId = acc.Id, FirstName = 'Test', LastName = 'Contact1');
        insert cont;

        Case[] cas = new List<Case>();
        for (Integer i=0; i<20; i++) {
            Case cases = new Case(Subject = 'Tst Case', AccountId = testAcc.Id, ContactId = cont.Id, Status= 'New');
            cas.add(cases);
        }
        insert cas;

        for (Case c : cas) {
            c.Status = 'Progress';
        }
        update cas;

        Test.startTest();
        CaseStatusChangeBatch cst = new CaseStatusChangeBatch();
        Database.executeBatch(cst);
        Test.stopTest();
    }
}