I need to write a apex batch class and schedulable class to run every day which sends a email notification using an email template. The condition is that whenever LastModifiedDate field from Opportunity field is less a year from today the email needs to be sent to the opportunity owner

Here's what I've come up with so far.

Batch class -

global class BatchInactiveOpps implements Database.Batchable<sObject> {

    global Database.QueryLocator start(Database.BatchableContext BC)
    {
        return Database.getQueryLocator([SELECT CloseDate,Description,Id,LastModifiedDate FROM Opportunity WHERE LastModifiedDate < LAST_N_DAYS:365]);
    }

    global void execute(Database.BatchableContext BC, List<Opportunity> scope)
    {
    	List<Messaging.SingleEmailMessage> mailsToSend = new List<Messaging.SingleEmailMessage>();
        for(Opportunity opp:scope){
			//TBD
			EmailTemplate template = [SELECT id FROM EmailTemplate WHERE DeveloperName = 'Opportunity_about_to_expire_template'];
			Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
            mail.setTemplateId(template.Id);
            mail.saveAsActivity = false;
            mailsToSend.add(mail);
            System.debug(opp.Name);
        }
        //Send Email
		if(mailsToSend.size() > 0){
    		Messaging.sendEmail(mailsToSend);       
		}
    }
    
    global void finish(Database.BatchableContext BC)
    {
    }
}

Schedulable class

global class SchedulableInactiveOpps implements Schedulable
{
    global void execute(SchedulableContext sc)
    { 
		Id InactiveOpps=Database.executeBatch(new BatchInactiveOpps());
    }
}

Test class

@isTest(SeeAllData=true)
public class TestemailonDuedate {
	public static testMethod void unitTest(){
		Test.startTest();
		EmailTemplate template = [SELECT id FROM EmailTemplate WHERE DeveloperName = 'Opportunity_about_to_expire_template'];
		Task tsk=new Task();
			tsk.ActivityDate=System.Today();
			tsk.Subject='Test';
			tsk.Status='In Progress';
			tsk.Priority='Normal';
			Insert tsk;
			System.assertEquals(tsk.Subject,'Test');

			emailonDuedate emailSch = new emailonDuedate();
			String sch = '0 0 23 * * ?'; 
			System.schedule('Test Territory Check', sch, emailSch); 
		Test.stopTest(); 
	}

}

Opportunity_about_to_expire_template is the email template i want to use while sending the email. 

Please let me know what changes needs to be done to the batch class and test class to make it work.