public void Test_calculate_sum_multiplied()
        {
            Example_class example = new Example_class();

            // make sure (2 + 2) * 2 = 8
            Assert.AreEqual(8,
                            example.Calculate_sum_multiplied(2, 2, 2));

            // make sure (2 + 3) * 5 = 25
            Assert.AreEqual(25,
                            example.Calculate_sum_multiplied(2, 3, 5));
        }