good evening dear community, when I'm trying to execute a test class it wont do it because it's telling me: 
System.QueryException: List has no rows for assignment to SObject

@isTest
private class HelperContactTriggerTestneu {
public static testMethod void myTestMethod() {


        Account acc = new Account(Name = 'Frau Test Test');
      
        {
        insert acc;

        List<Account> sendMail = [select id from account where id=:acc.id];
        test.startTest();

        HelperContactTrigger.sendEmail(sendMail);
        test.stopTest();
        
        }
        }
        }

it belongs to this class :

public with sharing class HelperContactTrigger {
    //static method
    public static List<Account> sendEmail(List<Account> accounts) {

        //query on template object
        EmailTemplate et=[Select id from EmailTemplate where name=:'Sales: New Customer Email'];

        //list of emails
        List<Messaging.SingleEmailMessage> emails = new List<Messaging.SingleEmailMessage>();

        //loop
        for(Account con : accounts){

            //check for Account
            if(con.PersonEmail == null && con.PersonEmail != null){

                //initiallize messaging method
                Messaging.SingleEmailMessage singleMail = new Messaging.SingleEmailMessage();

                //set object Id
                singleMail.setTargetObjectId(con.Id);

                //set template Id
                singleMail.setTemplateId(et.Id);

                //flag to false to stop inserting activity history
                singleMail.setSaveAsActivity(false);

                //add mail
                emails.add(singleMail);
            }
        }

        //send mail
        Messaging.sendEmail(emails);

        return accounts;
    }
}

I created these to automatically send an email when a new account has been inserted.
Any advices how to make it work at all? because otherwise i cant deploy my test class, thanks in advance!