GildedRose-Refactoring-Kata/YorkCodeDojo.md

YorkCodeDojo- The GildedRose

This is an exercise in handling changes in a legacy code base. Where legacy can mean a mix of low quality or missing automated tests, or poorly structured code and often both.

Have a read of the instruction given to you by your new employer to help add a new feature to stock management system at the GildedRose inn;

GildedRose Requirements

Your task

Your task is to handle a new type of stock item that is Conjured. Seems simple, until you look inside the main code base and it is a single large complex function with deep nesting…

Characterization tests

A strategy for dealing with systems like this is to use Characterization Tests;

“In computer programming, a characterization test (also known as Golden Master Testing[1]) is a means to describe (characterize) the actual behavior of an existing piece of software, and therefore protect existing behavior of legacy code against unintended changes via automated testing. This term was coined by Michael Feathers.[2]”

Note: Sometimes these are called Approval Tests

Getting started

S o what does this mean? Before refactoring and changing code we should capture its current behaviour, if it doesn’t have good automated tests.

There are many different languages that you can perform this exercise in the GildedRose repository. Pick your favorite. They all work in broadly the same way;

• They have an item record class with quality and sellIn integer fields
• They have a method that updates a list of items for the new quality and sellIn for the next day
• Don’t change the item class or the signature of the update method
• They have a basic unit test that doesn’t work
• They have a basic Approval Test that logs to a block of text the quality and sellIn of various items over a thirty day run. It compares the output with a previous run to validate they are the same. This can be used to validate that any changes you make have not introduced any change to the behaviour

So what next?

• Can you improve the update code to make it easier to understand and make changes to?
• Can you make it handle Conjured items?
• Do you need to add any addtional unit tests?

Note: There are gaps in the requirements and (at least) one defect in the implementation. But where the specification differs from the code, it is the code that is correct. It has been like that for years I have been told and no one has complained…