TDD Vending Machine

Objectives:

• Give and receive feedback on pairing behaviors - see Pairing Rubric below
• Practice writing tests first
• Practice writing good tests - transparent box, SEAT pattern
• Practice the ‘refactor’ of red, green, refactor
• Practice frequent commits with good messages

Setup

• Clone this repository
• npm install
• npm test

Instructions

1. This exercise is meant to be completed with pair programming. Discuss when you will change driving/navigating roles.
2. Use the acceptance criteria for the first story to write a failing test.
3. Write the simplest code needed to make the test pass.
4. Commit
5. Move on to the next user story and continue until all stories are completed.

User Stories

As a customer, I want to see that the vending machine has items, so that I can purchase them.

• Given that I approach the vending machine
• when I look at it,
• then I see items inside that I can buy
• seeSelections() returns an array of objects with item and price: [{'crisps': 'Rs 100'}, {'chocolate': 'Rs 350'}, {'mints': 'Rs 70'}]

As a customer, I want to know how much money I have deposited, so that I know what I can purchase.

• Given I am using the vending machine,
• when I insert money,
• then I see the total I have deposited on a screen.
• deposit(100) returns 'You have deposited Rs 100'
• The machine should accept bills in these amounts: 10, 20, 50, 100, 500

As a customer, I want to add additional money, so that I can use the denominations I have to purchase an item.

• Given I have deposited money in the vending machine,
• when I deposit additional money,
• then I see the new total on a screen.
• After depositing Rs 100, deposit(50) returns 'You have deposited Rs 150'

As a customer, I want to see a message if my item is unavailable, so that I can make another choice.

• Given I am using the vending machine,
• when I enter a code for an item that is unavailable,
• then I see a message that the item is unavailable.
• selectItem(code) returns 'The item you selected is unavailable'

As a customer, I want to see a message if my deposit is insufficient, so that I know to add more money.

• Given I have made a choice,
• when I have not deposited enough money for that item,
• then I see a message telling me how much more to deposit.
• selectItem(code) returns 'Your deposit is insufficient. Please add Rs 20 for this item'

As a customer, I want to receive change, so that I don’t pay more than the item costs.

• Given I have made a selection,
• when the item is delivered,
• then I receive correct change (in correct monetary units)
• selectItem(code) returns an object with the item and an array of bills {item: 'mints', change: [20, 10]}

As a customer, I want to receive my money back when I push the cancel button, so that I can change my mind.

• Given that I have deposited money,
• When I push the cancel button,
• Then I receive my money back
• cancel() returns {change: [100]}

As a customer, I want to know if the vending machine can make change, so that I can cancel my choice if it can't make change.

• Given I have deposited money and selected a choice,
• when the machine does not have correct change,
• then I see a message
• selectItem(code) returns 'Cannot return proper change. Please choose another item or cancel the transaction'

Methods:

• seeSelections() => array of objects with item and price
• deposit(denomination) => totalDeposit
• selectItem(code) => item + change || insufficient funds msg || insufficient change msg || item not available msg
• cancel() => totalDepositReturned

Pairing Rubric