public void Test_calculateBill_WithDuplicates()
        {
            string[] testBill = new string[] { "Cola", "Coffee", "Cola" };
            double   expected = 2;
            double   actual   = BillCalculator.calculateBill(testBill);

            Assert.AreEqual(expected, actual);
        }
        public void Test_calculateBill_WithEmpty()
        {
            string[] testBill = new string[] {};
            double   expected = 0;
            double   actual   = BillCalculator.calculateBill(testBill);

            Assert.AreEqual(expected, actual);
        }
        public void Test_calculateBill_Basic()
        {
            string[] testBill = new string[] { "Cola", "Coffee", "Cheese Sandwich" };
            double   expected = 3.5;
            double   actual   = BillCalculator.calculateBill(testBill);

            Assert.AreEqual(expected, actual);
        }