How to write test class for Scheduler /Schedulable class in Salesforce

Sample Batch job

global class AccountUpdateBatchJob implements Database.Batchable<sObject> 
{    
    global Database.QueryLocator start(Database.BatchableContext BC)     {
        String query = 'SELECT Id,Name FROM Account';                
        return Database.getQueryLocator(query);     
    }    
    global void execute(Database.BatchableContext BC, List<Account> scope)     {        
        for(Account a : scope)        
        {            
            a.Name = a.Name + 'Updated by Batch job';        
        }        
        update scope;       
    }    
    global void finish(Database.BatchableContext BC) {    }
}

Scheduler Class For Batch Apex

global class AccountUpdateBatchJobscheduled implements Schedulable 
{
    global void execute(SchedulableContext sc) 
    {
        AccountUpdateBatchJob b = new AccountUpdateBatchJob(); 
        database.executebatch(b);
    }
}

Test Class for Scheduler Class

@isTest private class AccountUpdateBatchJobscheduledTest {     static testmethod void schedulerTest()      {         String CRON_EXP = '0 0 0 15 3 ? *';                  // Create your test data         Account acc = new Account();         acc.name= 'test';         insert acc;                  Test.startTest();             String jobId = System.schedule('ScheduleApexClassTest',  CRON_EXP, new AccountUpdateBatchJobscheduled());             CronTrigger ct = [SELECT Id, CronExpression, TimesTriggered, NextFireTime FROM CronTrigger WHERE id = :jobId];             System.assertEquals(CRON_EXP, ct.CronExpression);             System.assertEquals(0, ct.TimesTriggered);         Test.stopTest();         // Add assert here to validate result     } }

Please check below post for Batch job
1) http://amitsalesforce.blogspot.com/2016/02/batch-apex-in-salesforce-test-class-for.html

Please check below post for more detail
1) https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_scheduler.htm


Thanks,
Amit Chaudhary