Welcome to the fifth and final unit of this course, focused on practicing the principles of Test Driven Development (TDD) using C++ and Google Test. We're going to continue building our ShoppingCart system by integrating even more sophisticated features into our class.

In this course, emphasis is placed on hands-on practice, where you'll receive requirements through tests, one at a time. Your task is to write tests AND implement code that makes each test pass, simulating a real-world TDD environment. In previous lessons, tests were provided to guide you, but now it's your turn to define them!

Remember to apply the core concepts of the Red-Green-Refactor cycle while completing these coding exercises. Ask questions if you need any clarification!

• Description: The cart should enforce a maximum quantity limit of 10 for a single type of item, preventing more than this allowed amount from being added.
• Details
  • Utilize the AddItem(item, quantity) method to add items to the cart.
  • Ensure an exception is raised when adding a quantity that exceeds the limit of 10 for a single item.
  • The exception should be of type std::invalid_argument with the message "Maximum quantity exceeded."
• Examples: Attempting to add 11 units of an item should throw a std::invalid_argument exception indicating "Maximum quantity exceeded."

• Description: When an item is added to the cart, it should be possible to retrieve that item's details using its ID, including the product information and the quantity in the cart.
• Details
  • Enable items to be added using the AddItem() method with specific IDs.
  • Ensure that GetItem(id) returns the correct item details, including the quantity, after being added to the cart.
• Examples: Adding a "Book" with ID 1 and price 10 and retrieving by ID 1 should return an object with Id: 1, Name: 'Book', Price: 10, Quantity: 1.

• Description: Applying a valid discount code should reduce the total price of items in the cart by the specified discount percentage.
• Details
  • Use the ApplyDiscountCode(code) method to apply a discount.
  • Support valid discount codes stored in a std::map, such as HOLIDAY25 for a 25% discount.
  • Update GetTotal() to reflect the discounted price.
• Examples: Applying the discount code 'HOLIDAY25' to a product "Book" with a price of 100 should reduce the total to 75.

• Description: The system should not accept invalid discount codes and should throw an appropriate exception when such a code is applied.
• Details
  • Ensure ApplyDiscountCode(code) checks against a list of valid codes.
  • Raise an exception of type std::invalid_argument with the message "Invalid discount code" if the code is not valid.
• Examples: Applying the discount code "INVALID" after adding an item should throw an error indicating the code is invalid.

• Description: When an item that already exists in the cart is added again, its quantity should increase without creating duplicates, and the total price should reflect the cumulative quantity.
• Details
  • Allow items to be added again using the AddItem() method without creating duplicates in the cart.
  • Ensure GetItem(id) returns the updated quantity after adding the same item.
  • Update the total price to reflect the cumulative quantity of the added items.
• Examples: Adding a "Book" priced at 200 twice should result in a quantity of 2 for that item, with the total updated price reflecting the double addition.

• Description: When adding more units to existing items in the cart, the total quantity should not exceed the predefined maximum limit.
• Details
  • Use the AddItem(item) method to add units to an existing item.
  • Ensure that adding a quantity which causes the total to exceed the maximum allowed quantity throws an exception of type std::runtime_error.
  • The exception message should be "Maximum quantity exceeded" when the quantity limit is breached.
• Example: Adding 3 units of an item with ID 1, named Book, priced at 200 to an existing 8 units should throw an error, as it exceeds the limit.

In this unit, you reviewed descriptions for more advanced test cases to expand the functionality of the ShoppingCart class using C++ and Google Test. The focus was on utilizing TDD practices for advanced features like handling non-existent items, applying discounts, and updating item quantities. With solidified TDD skills, let's proceed to write targeted test cases that capture essential functionality for a robust ShoppingCart class.

As you undertake these exercises, remember to engage in the Red-Green-Refactor cycle.

Great work! You're almost finished with this practice course and well on your way to mastering TDD techniques. Red! Green! Refactor!