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)

Transcript

1. Escaping
   The Tar Pit
   Ernesto Tagwerker (@etagwerker)
   RubyConf, November 2019
   

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2. ! Hi, I’m from Argentina
   I live in Philadelphia
   # I ❤ Open Source
   

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3. Founder &
   Software Engineer
   @OmbuLabs
   

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4. Founder &
   Software Engineer
   @fastrubyio
   

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5. Open Source
   Maintainer
   database_cleaner;
   bundler-leak; next_rails
   

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6. Inspiration
   

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7. Chapter 1:
   The Tar Pit
   

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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
   

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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
   

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10. We are in the tar pit or
    trying to avoid it
    

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11. View Slide

12. Tar Pit Symptoms
    > Projects running over budget
    

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13. Tar Pit Symptoms
    > Projects running over budget
    > Taking forever to ship small changes
    

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14. Tar Pit Symptoms
    > Projects running over budget
    > Taking forever to ship small changes
    > Sacrificing quality, increasing tech debt
    

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15. View Slide

16. Part 1: How to avoid
    the tar pit
    

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17. “THAT’D BE GREAT”
    BOSS: “IF YOU COULD COME IN ON THIS GREAT, LEGACY
    PROJECT AND MAINTAIN IT FROM NOW ON…”
    

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18. “THAT’D BE GREAT”
    CLIENT: “IF YOU COULD COME IN ON THIS GREAT, LEGACY
    PROJECT AND MAINTAIN IT FROM NOW ON…”
    

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19. CLIENT: “HOW LONG IS IT GOING TO TAKE?”
    

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20. “BECAUSE I NEED IT BY END OF DAY TODAY”
    CLIENT: “HOW LONG IS IT GOING TO TAKE?”
    

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21. How can we quickly
    assess code quality?
    

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22. Part 2: How to get out
    of the tar pit
    

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23. How can we gradually
    pay off technical debt?
    

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24. Part 1: Avoiding
    the tar pit
    

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25. View Slide

26. “It can’t be that hard. It’s a Ruby project.”
    

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27. How can we quickly assess
    code quality?
    

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28. Assessing Quality
    ✅ Paid Services
    ✅ Open Source Gems
    

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29. Assessing Quality
    ✅ Paid Services
    ➡ Open Source Gems
    

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30. Open Source Gems
    ✅ Static code analysis
    

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31. Open Source Gems
    ✅ Static code analysis
    ✅ Code coverage
    

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32. Open Source Gems
    ✅ Static code analysis
    ✅ Code coverage
    ✅ Code smells
    

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33. What is software
    quality anyway?
    

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34. There are hundreds of
    definitions
    

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35. “The degree to which a
    system, component, or
    process meets implicit and
    explicit requirements.” IEEE
    

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36. “It works as expected.”
    

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37. “It works as expected
    and it is not a PITA to
    maintain it.”
    

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38. ISO 9126-1 Software Quality Model
    ✅ Reliability
    ✅ Usability
    ✅ Efficiency
    ✅ Maintainability
    ✅ Portability
    

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39. ISO 9126-1 Software Quality Model
    ✅ Reliability
    ✅ Usability
    ✅ Efficiency
    ➡ Maintainability
    ✅ Portability
    

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40. Maintainability
    

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41. Maintainability
    1. Code Coverage
    

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42. Maintainability
    1. Code Coverage
    2. Code Quality
    

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43. Code Coverage
    SimpleCov
    (github.com/colszowka/simplecov)
    

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44. Code Coverage
    # Gemfile
    group :test do
    gem "simplecov", require: false
    end
    

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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
    

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46. Code Coverage
    $ COVERAGE=true rspec
    

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47. Code Coverage
    

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48. Code Quality
    n options
    

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49. Code Quality
    n options (flog; flay; reek;
    churn; RubyCritic; MetricFu;
    attractor; rubocop;
    fukuzatsu; turbulence; …)
    

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50. Code Quality
    RubyCritic
    (github.com/whitesmith/rubycritic)
    

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51. Churn
    

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52. Churn
    git
    

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53. Churn
    $ git log --follow --format=%h default.rb | cat
    573c8f5
    2ccc5b8
    b447bc3
    

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54. Churn
    $ git log --follow --format=%h default.rb | cat
    573c8f5
    2ccc5b8
    b447bc3
    # Churn Count = 3
    

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55. Complexity
    

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56. Complexity
    flog
    

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57. Complexity
    $ flog foo.rb
    => 10.8: flog total
    

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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
    

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59. Complexity
    $ flog foo.rb
    => 10.8: flog total
    

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60. Churn
    vs.
    Complexity
    

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61. Churn
    Complexity
    50
    0
    1 100_000
    

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62. Churn
    Complexity
    100
    0
    1 100_000
    user.rb (changed: 2 times; complexity: 100_000 )
    

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63. Churn
    Complexity
    100
    0
    1 100_000
    user.rb
    (changed: 27 times; complexity: 100)
    

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64. Code Quality
    $ gem install rubycritic
    

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65. Code Quality
    $ rubycritic
    

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66. View Slide

67. GPA Pie Graph
    Complexity (flog)
    Code Smells (reek)
    

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68. Churn vs.
    Complexity
    Churn (SCM)
    Complexity (flog)
    

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69. 100
    0
    1 100_000
    Complexity
    Churn
    

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70. 100
    0
    1 100_000
    Complexity
    Churn
    

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71. 100
    0
    1 100_000
    “Welcome to
    the good place.” ❤
    Complexity
    Churn
    

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72. 100
    0
    1 100_000
    No one understands
    these files but they
    work. So don’t change
    them.
    Complexity
    Churn
    

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73. 100
    0
    1 100_000
    “[…], if the code
    never changes, it's not
    costing us money.”
    Sandi Metz
    Complexity
    Churn
    

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74. 100
    0
    1 100_000
    Everybody
    understands these files
    but you need to
    change them often
    Complexity
    Churn
    

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75. 100
    0
    1 100_000
    Complexity
    Churn
    These modules are
    complex and change a
    lot… '
    

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76. 100
    0
    1 100_000
    Complexity
    Churn
    “Sometimes a class
    becomes so complex that
    refactoring seems too
    difficult.”
    Michael Feathers
    

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77. Are you getting into a tar
    pit, is it a dumpster fire, or
    have you found a project
    which is easy to maintain?
    

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78. 100
    0
    1 100_000
    Welcome to the tar pit.
    Complexity
    Churn
    

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79. Maintainability
    1. Code Coverage (SimpleCov)
    2. Code Quality (RubyCritic)
    

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80. Signal #1
    Code Coverage
    

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81. Signal #2
    Complexity
    

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82. Coverage & Complexity
    

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83. But what if we could
    calculate a new signal
    that combines both?
    

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84. Signal #3
    StinkScore
    

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85. StinkScore =
    f(code_quality, code_coverage)
    

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86. StinkScore =
    f(code_smells,
    code_complexity,
    code_coverage)
    

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87. Files which lack
    tests should be
    penalized
    

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

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

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

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91. foo.rb and bar.rb are
    equally stinky
    

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

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93. bar.rb
    complexity: 10
    smells: 10
    code_coverage: 100
    stink_score: 100
    (10*10)*1
    

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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
    

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95. foo.rb is
    considerably
    stinkier
    than bar.rb
    

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96. How can we automate
    this analysis?
    

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97. Skunk
    A Stink Score Calculator
    (github.com/fastruby/skunk)
    

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98. Skunk
    $ gem install skunk
    

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99. Skunk
    $ skunk
    

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101. View Slide

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)
     

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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)
     

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104. RubyCritic
     module RubyCritic
     class AnalysedModule
     def cost
     smells.map(&:cost).inject(0.0, :+) +
     (complexity / COMPLEXITY_FACTOR)
     end
     end
     end
     

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105. RubyCritic
     module RubyCritic
     class AnalysedModule
     def cost
     smells.map(&:cost).inject(0.0, :+) + # From Reek
     (complexity / COMPLEXITY_FACTOR)
     end
     end
     end
     

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106. RubyCritic
     module RubyCritic
     class AnalysedModule
     def cost
     smells.map(&:cost).inject(0.0, :+) + # From Reek
     (complexity / COMPLEXITY_FACTOR) # From Flog
     end
     end
     end
     

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107. Skunk
     module RubyCritic
     class AnalysedModule
     def stink_score
     return cost if perfect_coverage?
     cost * (PERFECT_COVERAGE - coverage.to_i)
     end
     end
     end
     

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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
     

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109. Skunk Warning
     > skunk-v0.3.1
     

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110. Skunk Warning
     > skunk-v0.3.1
     > COVERAGE=TRUE rake test
     

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111. Skunk Warning
     > skunk-v0.3.1
     > COVERAGE=TRUE rake test
     > feedback wanted
     

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112. Maintainability
     1. Code Coverage (SimpleCov)
     2. Code Quality (RubyCritic)
     3. StinkScore (Skunk)
     

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113. You are here:
     

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114. Part 2: Getting out
     of the tar pit
     

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115. So, where do we begin?
     

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116. removing files
     will decrease
     our stink_score
     

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117. Find Dead Code
     Coverband
     (github.com/danmayer/coverband)
     

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118. View Slide

119. refactoring
     complex files
     will decrease
     our stink_score
     

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120. 100
     0
     1 100_000
     Complexity
     Churn
     “Here be dragons.
     These modules are
     complex and
     change a lot…” '
     

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121. 100
     0%
     1 100_000
     Complexity
     Churn
     “Great
     candidates for
     refactoring
     (paying technical
     debt!)” #
     

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122. Churn vs. Complexity is
     not enough to prioritize
     

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123. Stink Score Table
     

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124. Refactor These Files:
     

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125. Refactor These Files:
     

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126. 100
     0
     1 100_000
     Complexity
     Churn
     git.rb
     

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127. 100
     0
     1 100_000
     Complexity
     Churn
     git_calculator.rb
     git_fetcher.rb
     refactor!
     git.rb
     

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128. 100
     0
     1 100_000
     Complexity
     Churn
     git_calculator.rb
     git_fetcher.rb
     

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129. Skunk
     $ skunk -b master
     Base branch (master) average stink score: 79.78
     Feature branch (refactor/git) average stink score: 71.79
     

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130. Skunk
     $ skunk -b master
     Base branch (master) average stink score: 79.78
     Feature branch (refactor/git) average stink score: 71.79
     10% better ( ( (
     

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131. writing tests
     for our app will
     decrease our
     stink_score
     

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132. Stink Score Table
     

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133. Write Tests Here:
     

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134. Skunk*
     $ skunk -b master
     Base branch (master) average stink score: 79.78
     Feature branch (refactor/git) average stink score: 71.79
     

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135. Time
     StinkScore Average
     100 (days)
     0
     1 100
     

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136. stink_score
     Code Coverage;
     Complexity; and
     Smells
     

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137. stink_score
     Your compass to
     get out of the
     tar pit
     

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138. Thank you!
     @etagwerker
     138
     Thank you!
     ‣ github.com/fastruby/skunk
     ‣ @OmbuLabs
     ‣ @fastrubyio
     ‣ @etagwerker
     

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139. Resources
     1. https://github.com/whitesmith/rubycritic
     2.https://github.com/colszowka/simplecov
     3.https://github.com/metricfu/metric_fu
     4.https://github.com/julianrubisch/attractor
     5.https://www.fastruby.io/blog/ruby/quality/code-quality-ruby-gems.html
     6.https://www.reddit.com/r/ruby/comments/2bq092/rubycritic/
     7.http://jakescruggs.blogspot.com/2008/08/whats-good-flog-score.html
     8.http://ruby.sadi.st/Flog.html
     9.http://ruby.sadi.st/Flay.html
     10.https://github.com/makaroni4/sandi_meter
     11.https://www.fastruby.io/blog/code-quality/intruducing-skunk-stink-score-
     calculator.html
     

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140. Resources
     1.https://codeclimate.com/blog/deciphering-ruby-code-metrics/
     2.https://www.stickyminds.com/article/getting-empirical-about-refactoring
     3.https://www.sandimetz.com/blog/2017/9/13/breaking-up-the-behemoth
     4.https://github.com/troessner/reek
     5.https://github.com/seattlerb/flay
     6.https://github.com/seattlerb/flog
     7.http://www.sqa.net/iso9126.html
     8.https://www.slideshare.net/mscottford/important-metrics-for-measuring-code-health
     9.https://dilbert.com/strip/2006-12-08
     10.https://www.fastruby.io/blog/ruby/quality/code-quality-ruby-gems.html
     11.https://www.fastruby.io/blog/code-quality/code-coverage/rubycritic-4-2-0-
     simplecov-support.html
     

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