public void Test_Cost_sum_result_with_3_elements()
        {
            //arrange
            int[] costArray = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 };
            int groupSize = 3;
            int[] expected = { 6, 15, 24, 21 };
            INumberSumHandler target = new StubNumberSumHandler();

            //Act
            int[] actual = target.add(costArray, groupSize);

            //Assert
            CollectionAssert.AreEqual(expected, actual);
        }
        public void Test_Revenue_sum_result_with_4_elements()
        {
            //Arrange
            int[] costArray = { 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 };
            int groupSize = 4;
            int[] expected = { 50, 66, 60 };
            INumberSumHandler target = new StubNumberSumHandler();

            //Act
            int[] actual = target.add(costArray, groupSize);

            //Assert
            CollectionAssert.AreEqual(expected, actual);
        }