Theatrical players - refactoring Kata

A refactoring kata done in several teams to understand Approval tests and how to refactor legacy code with :
- OOP paradigms
- FP paradigms

Transcript

1. @algrison
   @yot88
   Theatrical players
   refactoring Kata
   

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2. @algrison
   @yot88
   Clone
   https://github.com/emilybache/Theatrical-Players-
   Refactoring-Kata
   

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3. @algrison
   @yot88
   Objective
   • Learn how to refactor “legacy” code
   • Practice FP concepts
   Theatrical players refactoring Kata
   Exercise
   • Add an HTML output with the same information
   

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4. Will it be easy to do the exercise ?
   Why ?
   What do you think about this code ?
   https://github.com/emilybache/Theatrical-Players-Refactoring-Kata
   

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5. 40 lines
   

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6. Formatting
   Amount calculation
   Credits calculation
   

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7. Formatting
   Amount calculation
   Credits calculation
   BROKEN
   

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8. @algrison
   @yot88
   How to start ?
   

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10. @algrison
    @yot88
    Which kind of tests ?
    The code already exists and works :
    • Easiest way to add a regression test is to find some test data, exercise the code,
    and approve the result
    • Add approval tests / snapshot tests / Golden master
    

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11. @algrison
    @yot88
    Approval tests : Generate output
    Statement for BigCo
    Hamlet: $650.00 (55 seats)
    As You Like It: $580.00 (35 seats)
    Othello: $500.00 (40 seats)
    Amount owed is $1,730.00
    You earned 47 credits
    

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12. @algrison
    @yot88
    Approval tests :
    Create a test
    https://approvaltests.com/
    Statement for BigCo
    Hamlet: $650.00 (55 seats)
    As You Like It: $580.00 (35 seats)
    Othello: $500.00 (40 seats)
    Amount owed is $1,730.00
    You earned 47 credits
    StatementPrinterTests.exampleStatem
    ent.approved.txt
    

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13. @algrison
    @yot88
    Approval tests :
    Lines not covered
    

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14. @algrison
    @yot88
    Confidence in the tests
    Mutation testing
    

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15. @algrison
    @yot88
    Let’s refactor
    https://github.com/emilybache/Theatrical-Players-Refactoring-Kata
    

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16. @algrison
    @yot88
    Step by step (OO style)
    1) Extract the amount calculation
    • For example you can use the Strategy pattern
    o Tragedy & Comedy
    • You can also use some kind of factory to retrieve the correct impl.
    2) Extract the credits calculation
    3) Create a specific Printer implementation
    • print(Line)
    • print(Statement)
    

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17. @algrison
    @yot88
    1) Extract the amount calculation
    

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18. @algrison
    @yot88
    2) Extract the credits calculation
    

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19. @algrison
    @yot88
    3) Create a specific Printer implementation
    

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20. @algrison
    @yot88
    Putting whole together
    

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21. @algrison
    @yot88
    Step by step (FP style)
    1) Extract the amount calculation
    • Create dedicated functions for both types
    • Tragedy & Comedy
    • Build a map of these implementations
    2) Build a statement
    3) Run the pipeline
    • Iterate
    • Reduce
    • Format
    

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22. @algrison
    @yot88
    1) Extract the amount calculation
    

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23. @algrison
    @yot88
    2) Build a statement
    

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24. @algrison
    @yot88
    3) Run the pipeline
    

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25. @algrison
    @yot88
    Resources
    • https://www.praqma.com/stories/refactoring-kata/
    • https://github.com/emilybache/Theatrical-Players-Refactoring-Kata
    • https://approvaltests.com/
    • Strategy pattern
    • https://refactoring.guru/design-patterns/strategy
    

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