Gilded Rose Kata

Purpose:

This kata fictionalizes the experience of working with someone else's code. You'll probably groan when you first see the code provided to you. The amount of code isn't overwhelming, its the prefect balance to evoke the feeling, "I can't wait to re-write this cruft." It's suggested that you use Test Driven Development with this kata. Once done, read the **spoiler** section below to see if you had a similar experience or not.

Original posting: http://iamnotmyself.com/2011/02/13/refactor-this-the-gilded-rose-kata/  http://www.iamnotmyself.com/2011/02/13/RefactorThisTheGildedRoseKata.aspx

C#: https://github.com/NotMyself/GildedRose

Java : https://github.com/wouterla/GildedRose

Ruby : https://github.com/professor/GildedRose

I believe that the Gilded Rose Kata was developed by Terry Hughes and Bobby Johnson and presented to the SC community on 2/13/2011. 

Kata Text

Hi and welcome to team Gilded Rose. As you know, we are a small inn with a prime location in a prominent city ran by a friendly innkeeper named Allison. We also buy and sell only the finest goods. Unfortunately, our goods are constantly degrading in quality as they approach their sell by date. We have a system in place that updates our inventory for us. It was developed by a no-nonsense type named Leeroy, who has moved on to new adventures. Your task is to add the new feature to our system so that we can begin selling a new category of items. First an introduction to our system:

• All items have a SellIn value which denotes the number of days we have to sell the item
• All items have a Quality value which denotes how valuable the item is
• At the end of each day our system lowers both values for every item

Pretty simple, right? Well this is where it gets interesting:

• Once the sell by date has passed, Quality degrades twice as fast
• The Quality of an item is never negative
• “Aged Brie” actually increases in Quality the older it gets
• The Quality of an item is never more than 50
• “Sulfuras”, being a legendary item, never has to be sold or decreases in Quality
• “Backstage passes”, like aged brie, increases in Quality as it’s SellIn value approaches; Quality increases by 2 when there are 10 days or less and by 3 when there are 5 days or less but Quality drops to 0 after the concert

We have recently signed a supplier of conjured items. This requires an update to our system:

• “Conjured” items degrade in Quality twice as fast as normal items

Feel free to make any changes to the UpdateQuality method and add any new code as long as everything still works correctly. However, do not alter the Item class or Items property as those belong to the goblin in the corner who will insta-rage and one-shot you as he doesn’t believe in shared code ownership (you can make the UpdateQuality method and Items property static if you like, we’ll cover for you).

Carnegie Mellon University - Silicon Valley campus reflections

**Spoilers** Note: you probably want to read this section after doing the kata. 

1. Most of the students thought this was a great kata for practicing TDD.

We had a great conversation about  what is the best way to test this? A few started with a given initial state and looped through update quality man times. They found that their test cases were as complicated as the code they were testing. Often this code was hard to follow or read. Many tested the individual requirements to verify that when we go from state N to state N+1, a certain invariant still holds true. 

2. What is the purpose of the Goblin rule?

(I need to find my notes on the class response to this one.) Most agreed that it was ok to subclass item provided that you didn't touch the code in the item class. Just to be sure, I asked Terry this question and here is his answer: "basically if the goblin sees anything different inside the Item class, everyone dies"