Test Class for CustNotify and CustNotifyScheduledCron

TestCustNotify.cls

@isTest
public with sharing class TestCustNotify {
    @TestSetup
    static void insertNewOpportunity() {

        Account objAccount = new Account(Name = 'Test Acc1', BillingCity = 'Test City', BillingState = 'Test State', 
        BillingStreet = 'Test Street', BillingPostalCode = '12345', 
        BillingCountry = 'Test Country', Phone = '123456');
        
        insert objAccount;

        Opportunity objOpp = new Opportunity(Name = 'Test Opp', AccountId = objAccount.Id, StageName = 'Verbal Confirmation', CloseDate = Date.today());
        insert objOpp;
    }

    @IsTest
    static void methodTest() {
        Test.startTest();
        SchedulableContext sc = null;
        try {
            CustNotifyScheduledCron.execute(sc);
        }catch(Exception e) {
        }
        Test.stopTest();
    }      
}