public void GradePassWithFail()
        {
            var result = (PassFailClass.Grade(35)).ToLower();

            Assert.AreEqual("fail", result);
        }
        public void GradeInvalid()
        {
            var result = (PassFailClass.Grade(-2)).ToLower();

            Assert.AreEqual("invalid input", result);
        }
        public void GradePassWithPass()
        {
            var result = (PassFailClass.Grade(55)).ToLower();

            Assert.AreEqual("pass", result);
        }
        public void GradePassWithMerit()
        {
            var result = (PassFailClass.Grade(65)).ToLower();

            Assert.AreEqual("pass with merit", result);
        }
        public void GradePassWithDistinction()
        {
            var result = (PassFailClass.Grade(85)).ToLower();

            Assert.AreEqual("pass with distinction", result);
        }
        public void Mark39AndUnderFails()
        {
            var result = (PassFailClass.PassFail(39)).ToLower();

            Assert.AreEqual("fail", result);
        }
        public void Mark40AndOverPasses()
        {
            var result = PassFailClass.PassFail(41);

            Assert.AreEqual("Pass", result);
        }