public void ShouldGetCorrectlyOrderedListByCategory(string expected)
        {
            // Arrange
            // Act
            List <Payment> actualList = clientProcessor.OrderByCategory(customers[0]);
            string         actual     = "";

            foreach (var item in actualList)
            {
                actual += item.Category.Name;
            }
            // Assert
            Assert.Equal(expected, actual);
        }