public void AddYearsToAge_notNegative()
        {
            //Arrange
            var TestPerson = new RealPerson("Henk", 10);

            //Act
            TestPerson.AddYearsToAge(-1);
            int Result = TestPerson.Age;

            //Assert
            Assert.AreEqual(10, Result);
        }
        public void AddYearsToAge_notOlderThan100()
        {
            //Arrange
            var TestPerson = new RealPerson("Henk", 100);

            //Act
            TestPerson.AddYearsToAge(1);
            int Result = TestPerson.Age;

            //Assert
            Assert.AreEqual(100, Result);
        }