Refactoring When You Literally Can't Even

Refactoring is the process of changing the structure of a codebase without changing its external behavior. In addition to being an important part of ongoing development, it can also be used to get a legacy codebase under control.

Using the Gilded Rose Kata as a basis, this workshop explores how to refactor a legacy codebase safely, even when you don't yet understand what the code is doing.

Transcript

1. Workshop Setup
   Navigate to https://github.com/CodingZeal/gilded-rose-railsconf2015
   Click on the Nitrous QuickStart button
   Create a new account or Log in to your existing account
   

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2. www
   .codingzeal.com
   @codingzeal
   Randy Coulman
   a.k.a. Refactron
   Refactoring When You
   Literally Can’t Even
   Senior Software Engineer
   @randycoulman
   

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3. Welcome to our new job!
   Enhance the inventory management system
   for the Gilded Rose Inn
   

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4. The System
   • Sell_in: the number of days we have to
   sell the item
   • Quality: how valuable the item is
   • End of each day: lower both values for
   every item
   

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5. The Spec: Can We Trust It?
   • 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 its
   sell-by date 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.
   

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6. Constraint
   The Item class and @items property
   are off-limits
   No collective code ownership
   

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7. Our Task: Support Conjured items
   Conjured items degrade in quality
   twice as fast as normal items
   

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8. Workshop Structure
   Mix of:
   • Presentation
   • Mob programming
   • Small group/pair/individual work
   

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9. Mob Programming
   • One computer for programming
   • One driver
   • N navigators and researchers
   http://mobprogramming.org/mob-programming-basics/
   

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10. How to Change Code
    https://twitter.com/KentBeck/status/250733358307500032
    

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11. What is Refactoring?
    “a disciplined technique for restructuring
    an existing body of code, altering its
    internal structure without changing its
    external behavior”
    http://refactoring.com
    

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12. Refactoring
    

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13. Refactoring
    Many refactorings are mechanical
    

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14. When to Refactor?
    Get legacy code under control
    

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15. When to Refactor?
    An ongoing part of your workflow
    Test-Driven Development (TDD) Cycle:
    Red -> Green -> Refactor
    

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16. Why Refactor?
    Make the code reflect your current
    understanding of the system
    

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17. Why Refactor?
    Ideal: Make the code look like it would have
    looked if the feature you just added had
    always been there
    

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18. Refactoring
    Requires test coverage
    

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19. Refactoring Legacy Code
    The Scouting Rule:
    "Leave the campground cleaner
    than you found it"
    

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20. Refactoring Legacy Code
    Baby Steps
    Lots of tiny, safe refactorings
    add up to big changes
    

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21. Refactoring Legacy Code
    Don’t Boil the Ocean
    Stay focused on your task
    

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22. Refactoring Legacy Code
    https://twitter.com/supermoof/status/478322429257715712
    

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23. The Code
    

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24. Want More?
    Original Gilded Rose Kata
    http://craftsmanship.sv.cmu.edu/katas/gilded-rose-kata
    Gilding the Rose Talk at GoGaRuCo 2014
    http://confreaks.tv/videos/gogaruco2014-gilding-the-rose-refactoring-legacy-code
    Code from GoGaRuCo 2014 Talk
    https://github.com/randycoulman/GildedRose
    

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25. References
    Working Effectively With Legacy Code:
    Michael Feathers
    http://www.amazon.com/Working-Effectively-Legacy-Michael-Feathers/dp/0131177052
    Refactoring: Martin Fowler
    http://www.amazon.com/Refactoring-Improving-Design-Existing-Code/dp/0201485672
    Refactoring Ruby Edition: Jay Fields, Shane
    Harvie, and Martin Fowler
    http://www.amazon.com/Refactoring-Ruby-Jay-Fields/dp/0321603508
    

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26. Questions ?
    http://randycoulman.com
    Code is on Github
    https://github.com/CodingZeal/gilded-rose-railsconf2015
    Slides Are on Speakerdeck
    https://speakerdeck.com/randycoulman
    

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27. www
    .codingzeal.com
    @codingzeal
    Thank You!
    Randy Coulman
    @randycoulman
    

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