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
2. @algrison @yot88 Clone https://github.com/emilybache/Theatrical-Players- Refactoring-Kata
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
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
5. 40 lines
6. Formatting Amount calculation Credits calculation
7. Formatting Amount calculation Credits calculation BROKEN
8. @algrison @yot88 How to start ?
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
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
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
13. @algrison @yot88 Approval tests : Lines not covered
14. @algrison @yot88 Confidence in the tests Mutation testing
15. @algrison @yot88 Let’s refactor https://github.com/emilybache/Theatrical-Players-Refactoring-Kata
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)
17. @algrison @yot88 1) Extract the amount calculation
18. @algrison @yot88 2) Extract the credits calculation
19. @algrison @yot88 3) Create a specific Printer implementation
20. @algrison @yot88 Putting whole together
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
22. @algrison @yot88 1) Extract the amount calculation
23. @algrison @yot88 2) Build a statement
24. @algrison @yot88 3) Run the pipeline
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