goblineer / tdd-exercise

TDD Exercise

In this exercise you will write a method and set of tests in TDD fashion which calculates a hand's BlackJack score.

About BlackJack

In the card BlackJack each card has a value.

• Number cards (2-10) carry the card's numeric value.
• Face cards on the other hand ("Jack", "Queen", "King") have a value of 10.
• Aces (1) can have a value of either 1 or 11, whichever will get the hand closest to 21 without going over.

For example if I had a 3, a King, and an Ace, my BlackJack score is 14 (3 + 10 + 1). If I have an Ace, and a Jack then my score is 21 (11 + 10).

A hand, an array of Card values, must be between 2 and 5 items inclusive.

When a hand's score is greater than 21, the hand is a bust and the player automatically loses.

Part 1: Identifying Edge & Nominal Cases

With a partner talk through the following questions and write down answers.

1. What would be two nominal cases?
2. What edge cases can you determine? Name at least 3.
3. How would you test these cases?

When you finish talk with another pair and walk through your answers.

Part 2: Calculating a Score

You will write a method called: blackjack_score which take an array of card values and returns the blackjack score. The card values can be any of the following, number values 1-9, "King", "Queen", "Jack". If the array contains an invalid card value or the total exceeds 21, raise an ArgumentError. For example blackjack_score([1, 5, 3]) will return 19. You should also raise an error if the hand contains more than 5 cards.

In this exercise you will complete the given tests in specs/blackjack_score_specs.rb and updating the blackjack_score method in lib/blackjack_score.rb to make it pass.

Step 1: Complete the given test Step 2: Update blackjack_score to pass the test Step 3: Move to the next test