Confident refactors

Transcript

1. Confident Refactors

2. Mehdi Lahmam @mehlah

3. 25kV Rails app, started in Feb 2009 Never rewritten 23k+

   commits from 52 contributors

4. Ruby is a massively successful language!

5. Early success Making it easy to make new things

6. Later success Making it easy to maintain old things

7. Today, let’s refactor some legacy code

8. Today, let’s refactor some legacy code

9. Refactor - verb To change the design of code without

   changing its observable behavior.

10. Refactor - verb To change in advance of a new

    feature or bug fix, making the job easier.

11. Today, let’s refactor some legacy code

12. Legacy - noun Old code.

13. Legacy - noun Code without tests.

14. Legacy - noun Code that we don’t like.

15. Legacy - noun Code we don’t understand well enough
 to

    change confidently.

16. Today, let’s refactor some legacy code

17. Refactoring is hard

18. Refactoring legacy code is very hard

19. Easy to accidentally break functionality

20. Legacy refactors feels unsafe

21. Legacy refactors are hard to sell

22. Business priority Cost / risks

23. Business priority Cost / risks New features

24. Business priority Cost / risks New features Bugs fixes

25. Business priority Cost / risks New features Bugs fixes Testing

26. Business priority Cost / risks New features Bug fixes Testing

    Refactoring

27. Business priority Cost / risks New features Bug fixes Testing

    Refactoring no selling needed easy to sell can often sell very hard to sell

28. Selling refactoring is hard ⏲ ⛔

29. Business priority Cost / risks Refactoring

30. Too much pressure ⏳ ⚒

31. Refactors are scary

32. What techniques we have? PDD - Pray Driven Development Fowler’s

    refactoring book Characterization testing A/B testing, experiments

33. Refactors as surgeries

34. Refactors as surgeries Requires careful planning Follow a clear process

    Multiple observations Flexible tools Things can get bloody

35. 1. Plan 2. Cut 3. Record 4. Validate 5. Refactor

    6. Verify 7. Compare 8. Fallback 9. Delete Clear process
36. None
37. None
38. None

39. Cut

40. Record

41. Validate ✅

42. Refactor <Insert magic here />

43. Verify

44. Compare ⚖

45. Fallback

46. Delete ✂

47. We dit it

48. We dit it Time to celebrate hard