In this exercise you will write a method and set of tests in TDD fashion which calculates a hand's BlackJack score.
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.
With a partner talk through the following questions and write down answers.
- What would be two nominal cases?
- What edge cases can you determine? Name at least 3.
- How would you test these cases?
When you finish talk with another pair and walk through your answers.
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 test/blackjack_score_test.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