Katas

Shopping cart

Written by Emmanuel Valverde | Jan 28, 2023 9:00:00 AM

What do we want to build?

We are building a shopping cart for an online grocery shop.  The idea of this kata is to build the product in an iterative way.

Technical requirements

  • The price per unit is calculated based on the product cost and the percentage of revenue that the company wants for that product.
  • The price has to be rounded up; so if a price per unit calculated is 1.7825, then the expected price per unit for that product is 1.79
  • The final price of the product is then calculated as the price per unit with the VAT rounded up.
  • Products are not allowed to have the same name.

List of products

Name Cost % Revenue Price per unit Tax Final price
Iceberg 🥬 1.55 € 15 % 1,79 € Normal (21%) 2.17 €
Tomato 🍅 0.52 € 15 % 0.60 € Normal (21%) 0.73 €
Chicken 🍗 1.34 € 12 % 1.51 € Normal (21%) 1.83 €
Bread 🍞 0.71 € 12 % 0.80 € First necessity (10%) 0.88 €
Corn 🌽 1.21 € 12 % 1.36 € First necessity (10%) 1.50 €

List of discounts

Discounts code Amount
PROMO_5 5%
PROMO_10 10%

 

Use cases

List the shopping cart

As customer
I want to see my shipping cart

Empty cart

--------------------------------------------
| Product name | Price with VAT | Quantity |
| -----------  | -------------- | -------- |
|------------------------------------------|
| Promotion:                               |
--------------------------------------------
| Total productos: 0                       |
| Total price: 0.00 €                      |
--------------------------------------------

Add product to shopping cart

As customer
I want to add Iceberg 🥬 to my shipping cart
I want to add Tomatoe 🍅 to my shipping cart
I want to add Chicken 🍗 to my shipping cart
I want to add Bread 🍞 to my shipping cart
I want to add Corn 🌽 to my shipping cart
I want to see my shipping cart
--------------------------------------------
| Product name | Price with VAT | Quantity |
| -----------  | -------------- | -------- |
| Iceberg 🥬   | 2.17 €         | 1        |
| Tomatoe 🍅   | 0.73 €         | 1        |
| Chicken 🍗   | 1.83 €         | 1        |
| Bread 🍞     | 0.88 €         | 1        |
| Corn 🌽      | 1.50 €         | 1        |
|------------------------------------------|
| Promotion:                               |
--------------------------------------------
| Total productos: 5                       |
| Total price: 7.11 €                      |
--------------------------------------------

Add product to shopping cart

As customer
I want to add Iceberg 🥬 to my shipping cart
I want to add Iceberg 🥬 to my shipping cart
I want to add Iceberg 🥬 to my shipping cart
I want to add Tomatoe 🍅 to my shipping cart
I want to add Chicken 🍗 to my shipping cart
I want to add Bread 🍞 to my shipping cart
I want to add Bread 🍞 to my shipping cart
I want to add Corn 🌽 to my shipping cart
I want to see my shipping cart

 

--------------------------------------------
| Product name | Price with VAT | Quantity |
| -----------  | -------------- | -------- |
| Iceberg 🥬   | 2.17 €         | 3        |
| Tomatoe 🍅   | 0.73 €         | 1        |
| Chicken 🍗   | 1.83 €         | 1        |
| Bread 🍞     | 0.88 €         | 2        |
| Corn 🌽      | 1.50 €         | 1        |
|------------------------------------------|
| Promotion:                               |
--------------------------------------------
| Total productos: 8                       |
| Total price: 12.33 €                     |
--------------------------------------------

 

Apply discount to the shopping cart

As customer
I want to add Iceberg 🥬 to my shipping cart
I want to add Iceberg 🥬 to my shipping cart
I want to add Iceberg 🥬 to my shipping cart
I want to add Tomatoe 🍅 to my shipping cart
I want to add Chicken 🍗 to my shipping cart
I want to add Bread 🍞 to my shipping cart
I want to add Bread 🍞 to my shipping cart
I want to add Corn 🌽 to my shipping cart
I want to apply my coupon code PROMO_5
I want to see my shipping cart
--------------------------------------------
| Product name | Price with VAT | Quantity |
| -----------  | -------------- | -------- |
| Iceberg 🥬   | 2.17 €         | 3        |
| Tomatoe 🍅   | 0.73 €         | 1        |
| Chicken 🍗   | 1.83 €         | 1        |
| Bread 🍞     | 0.88 €         | 2        |
| Corn 🌽      | 1.50 €         | 1        |
|------------------------------------------|
| Promotion: 5% off with code PROMO_5      |
--------------------------------------------
| Total productos: 8                       |
| Total price: 11.71 €                     |
--------------------------------------------

Possible API for the ShoppingCart

You could change this API this is only for example purposes.

Approach 1 passing objects as arguments could be DTO

public interface ShoppingCart {
    public void addItem(Product product);
    public void deletItem(Product product);
    public void applyDiscount(Discount discount)
    public void printShoppingCart();
}

Approach 2 passing primitives as arguments
 
public interface ShoppingCart {
    public void addItem(String productName);
    public void deletItem(String productName);
    public void applyDiscount(Double discount)
    public void printShoppingCart();
}

Approach 3 passing primitives as arguments and returning a DTO

public interface ShoppingCart {
    public void addItem(String productName);
    public void deletItem(String productName);
    public void applyDiscount(Double discount)
    public ShoppingCartList getShoppingCart();
}

Disclaimer

The graphic examples that you see on the kata are not there to be implemented if you don't want to, are there as a reference of how the kata works
View full post