Welcome to your fifth and final unit for this course dedicated to practicing Test Driven Development (TDD) utilizing TypeScript and Jest. We're going to finish building a our ShoppingCart system by adding even more 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. Where I wrote the tests for you last time, this time it's all up to you!

Remember to use the core concepts of the Red-Green-Refactor cycle while completing these coding exercises. I'm still here to help! Just ask.

• Description: The cart should enforce a maximum quantity limit of 10 for a single type of item, preventing more than the allowed amount to be added.
• Details
  • Utilize the addItem(item, quantity) method to add items to the cart.
  • Ensure an error is raised when adding a quantity that exceeds a limit of 10 for a single item.
  • The error message should clearly state 'Maximum quantity exceeded' when the limit is breached.
• Examples: Attempting to add 11 units of { id: '1', name: 'Book', price: 10 } should throw an error indicating 'Maximum quantity exceeded'.

• Description: When an item is added to the cart, it should be possible to retrieve the item details using its ID, which includes the product information and its quantity in the cart.
• Details
  • enable items to be added using an addItem() method with specific IDs
  • ensure getItem(id) returns the correct item details, including the quantity after being added to the cart
• Examples: adding { id: '1', name: 'Book', price: 10 } and retrieving by ID 1 should return { 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 applyDiscountCode(code) method to apply discount
  • support valid discount codes like 'HOLIDAY25' for a 25% discount
  • update getTotal() to reflect the discounted price
• Examples: applying the discount code 'HOLIDAY25' to an item { id: '1', name: 'Book', price: 100 } should reduce the total to 75

• Description: The system should not accept discount codes that are invalid and should throw an appropriate error when such a code is applied.
• Details
  • ensure applyDiscountCode(code) checks against a list of valid codes
  • raise an error 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 errorindicating the code is invalid.

• Description: When an item that already exists in the cart is added again, its quantity should increase without duplicates, and the total price should reflect the cumulative price.
• 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 price of the added items' cumulative quantities.
• Examples: Adding { id: '1', name: 'Book', price: 200 } twice should result in a quantity of 2 for that item, with the total updated price reflecting the double addition.

• Description: When an existing item in the cart has more units added to it, the total quantity should not exceed the predefined maximum limit.
• Details
  • Utilize the addItem(item) method to add to an existing item.
  • Ensure that adding a quantity which results in exceeding the maximum allowed quantity throws an error.
  • The error message should be 'Maximum quantity exceeded' when the quantity limit is breached.
• Example: Adding 3 units of { id: '1', name: 'Book', price: 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, covering features like handling non-existent items, applying discounts, and updating item quantities. With the solidified TDD skills, let's proceed to writing 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. Be sure to practice writing tests first and do not write implementation code unless the test asks for it.

And you're almost done with this practice course! Great work! You're almost there.

Red! Green! Refactor!