Escaping The Tar Pit at RubyConf 2019

Escaping The Tar Pit at RubyConf 2019

Presentation about avoiding and escaping the tar pit. The case for a new metric: The StinkScore.

The StinkScore is a combination of smells; complexity; and code coverage. You can use it as a compass to get out of the tar pit and gradually (and measurably) pay off technical debt. 🤓❤️

Presented at RubyConf in Nashville (Nov 19th, 2019)

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Ernesto Tagwerker

November 19, 2019
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Transcript

  1. 8.

    “The fiercer the struggle, the more entangling the tar, and

    no beast is so strong or so skillful but that they ultimately sink.” Fred Brooks
  2. 9.

    “Large-system programming has over the past decade been such a

    tar pit, and many great and powerful beasts have thrashed violently in it.” Fred Brooks
  3. 11.
  4. 14.

    Tar Pit Symptoms > Projects running over budget > Taking

    forever to ship small changes > Sacrificing quality, increasing tech debt
  5. 15.
  6. 17.

    “THAT’D BE GREAT” BOSS: “IF YOU COULD COME IN ON

    THIS GREAT, LEGACY PROJECT AND MAINTAIN IT FROM NOW ON…”
  7. 18.

    “THAT’D BE GREAT” CLIENT: “IF YOU COULD COME IN ON

    THIS GREAT, LEGACY PROJECT AND MAINTAIN IT FROM NOW ON…”
  8. 20.

    “BECAUSE I NEED IT BY END OF DAY TODAY” CLIENT:

    “HOW LONG IS IT GOING TO TAKE?”
  9. 25.
  10. 35.

    “The degree to which a system, component, or process meets

    implicit and explicit requirements.” IEEE
  11. 38.

    ISO 9126-1 Software Quality Model ✅ Reliability ✅ Usability ✅

    Efficiency ✅ Maintainability ✅ Portability
  12. 39.

    ISO 9126-1 Software Quality Model ✅ Reliability ✅ Usability ✅

    Efficiency ➡ Maintainability ✅ Portability
  13. 45.

    Code Coverage # spec/spec_helper.rb if ENV["COVERAGE"] == "true" require 'simplecov'

    SimpleCov.start do add_group "Models", "models" add_filter "/spec/" track_files "**/*.rb" end end
  14. 49.

    Code Quality n options (flog; flay; reek; churn; RubyCritic; MetricFu;

    attractor; rubocop; fukuzatsu; turbulence; …)
  15. 51.
  16. 52.
  17. 58.

    Complexity class Foo def yay # 10.8 = a =

    eval "1+1" # 1.2 + 6.0 + if a == 2 # 1.2 + 1.2 + puts "yay" # 1.2 end end end
  18. 66.
  19. 72.

    100 0 1 100_000 No one understands these files but

    they work. So don’t change them. Complexity Churn
  20. 73.

    100 0 1 100_000 “[…], if the code never changes,

    it's not costing us money.” Sandi Metz Complexity Churn
  21. 74.

    100 0 1 100_000 Everybody understands these files but you

    need to change them often Complexity Churn
  22. 76.

    100 0 1 100_000 Complexity Churn “Sometimes a class becomes

    so complex that refactoring seems too difficult.” Michael Feathers
  23. 77.

    Are you getting into a tar pit, is it a

    dumpster fire, or have you found a project which is easy to maintain?
  24. 90.

    foo.rb complexity: 10 smells: 10 smell points: 100 (10*10) bar.rb

    complexity: 10 smells: 10 smell points: 100 (10*10)
  25. 94.

    foo.rb complexity: 10 smells: 10 code_coverage: 0 stink_score: 10,000 (10*10)*100

    bar.rb complexity: 10 smells: 10 code_coverage: 100 stink_score: 100 (10*10)*1
  26. 100.
  27. 101.
  28. 102.

    Skunk $ skunk ... StinkScore Total: 13231.069999999996 Modules Analysed: 71

    StinkScore Average: 186.3530985915493 Worst StinkScore: 2401.75 (lib/rubycritic/source_control_systems/git.rb)
  29. 103.

    Skunk $ skunk ... StinkScore Total: 13231.069999999996 Modules Analysed: 71

    StinkScore Average: 186.3530985915493 Worst StinkScore: 2401.75 (lib/rubycritic/source_control_systems/git.rb)
  30. 105.
  31. 106.

    RubyCritic module RubyCritic class AnalysedModule def cost smells.map(&:cost).inject(0.0, :+) +

    # From Reek (complexity / COMPLEXITY_FACTOR) # From Flog end end end
  32. 107.

    Skunk module RubyCritic class AnalysedModule def stink_score return cost if

    perfect_coverage? cost * (PERFECT_COVERAGE - coverage.to_i) end end end
  33. 108.

    Skunk module RubyCritic class AnalysedModule def stink_score return cost if

    perfect_coverage? cost * (PERFECT_COVERAGE - coverage.to_i) # Penalty Factor = 100% - 20% => 80 end end end
  34. 118.
  35. 120.

    100 0 1 100_000 Complexity Churn “Here be dragons. These

    modules are complex and change a lot…” '
  36. 129.

    Skunk $ skunk -b master Base branch (master) average stink

    score: 79.78 Feature branch (refactor/git) average stink score: 71.79
  37. 130.

    Skunk $ skunk -b master Base branch (master) average stink

    score: 79.78 Feature branch (refactor/git) average stink score: 71.79 10% better ( ( (
  38. 134.

    Skunk* $ skunk -b master Base branch (master) average stink

    score: 79.78 Feature branch (refactor/git) average stink score: 71.79