gistfile1.cls

public with sharing class BusinessHoursClass_Test{

  static testMethod void holidayShouldNotIncludeBusinessHours(){
    BusinessHours supportHours = BusinessHoursClass.getBusinessHoursMap().get('GSO Salesforce Support');
    Time midnight = Time.newInstance(0,0,0,0);

    Date startDate = Date.newInstance(2013,12,24);
    DateTime pacificStartDateTime = DateTime.newInstance(startDate,midnight);
    Date pacificStartDate = date.valueOf(pacificStartDateTime);

    Date endDate  = Date.newInstance(2013,12,25);
    DateTime pacificEndDateTime = DateTime.newInstance(endDate, midnight);
    Date pacificEndDate = Date.valueOf(pacificEndDateTime);
    integer businessHours = BusinessHoursClass.hoursBetween(supportHours.id, pacificStartDate, pacificEndDate);
    system.assertEquals(0, businessHours);
  }
}