sachix1001/mini.tdd-vending-machine

TDD Vending Machine

This was created during my time as a Code Chrysalis Student

Practice pairing and test-driven development skills as you create a vending machine.

Objectives

In this task you will:

• Use test-driven development to create a state machine
• Practice writing tests before code
• Practice using the SEAT pattern for tests
• Practice effective pairing techniques

User story

• As a shopper,
• I would like to have a vending machine
• So that I can buy goods efficiently.

State

• balance - the amount of money currently inserted but not yet used
• till - a map of coins and counts in the machine
• selectedRow - stores the row selected, if any
• selectedColumn - stores the selected column, if any

Behavior

Please note that these are suggestions for methods, you will probably have an easier time adding more than these methods to make testing easier. Remember: Single Responsibility Principle, a method should only do 1 thing.

• insertCoin(denomination) - to put a coin in the machine
• changeReturn() - logs the coins to the console and resets the balance
• pressButton('A'-'D') - select a row
• pressButton(1-4) - select a column

Instructions

Model the products as a 4x4 array of arrays containing your favorite products, with a name and price, eg:

const juice = {name: `Apple Juice`, price: 350, count: 5};
const coffee = {name: "Tully's", price: 250, count: 7};

const inventory = [
  [juice, coffee, ..., ...],
  [..., ..., ..., ...],
  [..., ..., ..., ...],
  [..., ..., ..., ...],
]

The happy path should proceed as follows:

1. Insert coins
2. Select a row
3. Select a column
4. Dispense the product (log to console)
5. Update the inventory
6. Dispense change

Acceptance criteria

1. Given that the balance is zero, when a coin is inserted, then the balance should rise and types of coins should be stored
2. Given that no row is selected, when a row is selected the letter should be saved and printed to the console
3. Given that a row is selected, when there is sufficient balance and inventory and a column is selected
   1. then the row and column should be logged to the console
   2. and a message should be logged stating "Here is your [item name]"
   3. and the item inventory should decrease by 1
   4. and the correct change should be returned (log type and number of coins to console)
4. Given that a row and column are selected, when there is no inventory at that column, then an error message should be logged.
5. Given that a row and column are selected, when the balance is insufficient to purchase the selected item, then an error message should be printed
6. Given that the program has just started, when the balance is read, then it should read zero

Please note: you must track both the types of coins and number of coins to compute the balance and return change

Unhappy paths

At minimum, you must implement tests for all the acceptance criteria, however should not limit yourself to only these tests. Write as many tests as needed.

As a good TDD developer, when you find an edge case outside the specs, you should ask your PM (instructor) what the desired functionality should be.

Pairing

Take this opportunity to practice ping-pong pairing:

1. The pair on the left writes a failing test
2. The pair on the right writes the minimum code to make it pass
3. Righty then writes the next test
4. Lefty gets the test to pass

Don't forget to refactor, and only do so when green!

Hint: do not try to test what is being logged to console, instead think about how to structure your methods and have them return objects for things such as returned change or dispensed item, this then allows you to test the return value

Setup

yarn
yarn test