How to create unit test for the following linq query

public int CalculateRating(string hotelID)
     {
         var RatingQuery = from a in db.tbl_Reviews
                           where a.HotelID == hotelID
                           group a by a.HotelID into g
                           select new
                           {
                               TotalRating = g.Sum(a => a.Rating)
                           };
         int totalRating = Convert.ToInt16(RatingQuery.FirstOrDefault().TotalRating);

        int totalnoofRating = db.tbl_Reviews.Count(n => n.HotelID == hotelID);

        int newrating = (totalRating / totalnoofRating);

        return (newrating);
     }