public void ComputeLowestGrade()
        {
            GradeBook book = new GradeBook();

            book.AddGrade(90);
            book.AddGrade(30);

            GradeStats stats = book.ComputeStats();

            Assert.AreEqual(30, stats.LowestGrade);
        }
        public void ComputeAverageGrade()
        {
            GradeBook book = new GradeBook();

            book.AddGrade(90);
            book.AddGrade(80);
            book.AddGrade(30);

            GradeStats stats = book.ComputeStats();

            Assert.AreEqual(66.66f, stats.AverageGrade, 0.01f);
        }