System.Globalization.ThaiBuddhistCalendar.GetDaysInMonth C# (CSharp) Method

        public override int GetDaysInMonth(int year, int month, int era) {
            return (helper.GetDaysInMonth(year, month, era));
        }

 public void PosTest1()
 {
     System.Globalization.Calendar tbc = new ThaiBuddhistCalendar();
     Random rand = new Random(-55);
     int year = rand.Next(tbc.MinSupportedDateTime.Year + 543, tbc.MaxSupportedDateTime.Year + 544);
     int month = rand.Next(1, 13);
     int day = rand.Next(1, tbc.GetDaysInMonth(year, month) + 1);
     DateTime dt = tbc.ToDateTime(year, month, day, 0, 0, 0, 0);
     int era = tbc.GetEra(dt);
     Assert.Equal(1, era);
 }