You have to test multiple versions of your gem's dependencies. You used Appraisal. It's super affective!

So, it seems like you've finished writing your awesome gem. However, are you sure that your gem is working perfectly against multiple versions of its dependency? Are you sure that you didn't break any backward compatibility? In this talk, I'm going to show you the approach we have been taken to test our gems against multiple versions of dependencies, such as testing against Rails 3.2 and Rails 3.1. I'm also going to introduce you to our gem called "Appraisal" which helps you generating Gemfiles to be used with Bundler, and also guide it to running your test suite against those multiple Gemfiles. Lastly, I'm going to show you how you can config Travis CI to test your gem against those multiple versions of dependencies.

Presented at RubyKaigi 2013 on May 30, 2013.

Video is available at http://vimeo.com/69748748

Transcript

1. You have to test multiple versions
   of your gem’s dependencies.
   You used Appraisal. It’s super effective!
   

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2. ϖϨϜɹγνϟψΪτ
   Prem Sichanugrist
   Developer at thoughtbot
   @sikachu
   /sikachu
   

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3. View Slide

4. Published your gem?
   

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5. Fully tested?
   

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6. Works with older
   version of dependencies?
   

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7. Works with older
   version of dependencies?
   

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8. Why testing with
   multiple versions?
   

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9. People doesn’t update their
   project’s dependencies
   

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10. People install your gem
    

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11. Your gem is only tested
    against newer version
    of its dependency
    

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12. “This gem doesn’t work”
    

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14. Works with latest version
    !=
    Works with old versions
    

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15. ~>
    

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16. SemVer
    Semantic Versioning
    

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17. ~> 3.2
    

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18. ~> 3.2
    

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19. ~> 3.2
    

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20. People don’t follow
    SemVer
    

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21. People don’t follow
    SemVer
    

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23. Supported Rails Versions
    • 3.1.x
    • 3.2.x
    

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24. Supported Rails Versions
    • 3.1.x
    • 3.2.x
    • 4.0.0
    

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25. Supported Rails Versions
    • 3.0.x
    • 3.1.x
    • 3.2.x
    • 4.0.0
    

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26. Supported Rails Versions
    • 2.3.x
    • 3.0.x
    • 3.1.x
    • 3.2.x
    • 4.0.0
    

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27. How?
    

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28. Before Bundler
    

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29. Uninstall and reinstall
    

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30. $ gem uninstall activesupport
    $ gem install activesupport -v 3.1.12
    $ rake
    $ gem install activesupport
    $ rake
    

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31. ·͍ͣ
    (Bad)
    

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32. Why was this so bad?
    • Time consuming
    • Can’t test against multiple versions at once
    • Doesn’t handle dependency of dependency
    • Dependency hell
    • $ rm -Rf $GEM_HOME
    

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33. Test in isolation
    

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34. Gemset
    

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35. rbenv
    (with rbenv-gemset)
    

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36. $ rvm gemset create rails-3-2
    $ rvm gemset use rails-3-2
    $ gem install rails -v 3.2.13
    $ rake
    $ rvm gemset create rails-3-1
    $ rvm gemset use rails-3-1
    $ gem install rails -v 3.1.12
    $ rake
    # ...
    

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37. $ rvm @rails-3-1,@rails-3-2 do rake
    

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38. View Slide

39. This is good, but ...
    • Waste of space; gems are not shared
    • Contributors need to use Ruby manager
    that supports Gemset
    • May need to have bootstrap script to setup
    gemsets
    

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40. View Slide

41. Multiple Gemfiles
    

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42. !"" Gemfile
    !"" rails-3-1.gemfile
    !"" rails-3-2.gemfile
    ...
    

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43. rails-3-1.gemfile:
    source "http://rubygems.org"
    gem "rails", "~> 3.1.12"
    gem "rspec"
    

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44. rails-3-2.gemfile:
    source "http://rubygems.org"
    gem "rails", "~> 3.2.13"
    gem "rspec"
    

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45. $ bundle install --gemfile=rails-3-2.gemfile
    $ export BUNDLE_GEMFILE=rails-3-2.gemfile
    $ bundle exec rake
    $ bundle install --gemfile=rails-3-1.gemfile
    $ export BUNDLE_GEMFILE=rails-3-1.gemfile
    $ bundle exec rake
    

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46. View Slide

47. View Slide

48. Still hard to maintain
    

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49. Still have to edit
    Gemfiles by hand
    

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50. Have to specify
    dependencies over and over
    

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51. Adding new dependency
    

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52. Adding new dependency
    ... edit multiple files!
    

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53. No easy way to test all
    the versions at once
    

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55. “There should be a
    better way to do this”
    

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56. Appraisal
    

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57. Set multiple versions of
    dependencies in one place
    

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58. Merge dependencies
    and generate Gemfiles
    

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59. Setup environment for
    Bundler
    

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61. Demo
    

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62. Gemfile:
    source "http://rubygems.org"
    gem "rails"
    gem "rspec"
    gem "appraisal"
    

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63. Gemfile:
    source "http://rubygems.org"
    gemspec
    

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64. Appraisals:
    appraise "rails-3-1" do
    gem "rails", "~> 3.1.12"
    end
    appraise "rails-3-2" do
    gem "rails", "~> 3.2.13"
    end
    

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65. Rakefile:
    require "bundler/setup"
    require "appraisal"
    task "test" do
    # ...
    end
    

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66. Rakefile:
    require "bundler/setup"
    require "appraisal"
    task "test" do
    # ...
    end
    

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67. # Generate Gemfiles
    $ rake appraisal:gemfiles
    # Install dependencies
    $ rake appraisal:install
    

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68. # Run "test" task against all versions
    $ rake appraisal test
    # Run "test" task against a single version
    $ rake appraisal:rails-3-1 test
    

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69. Appraisal
    • Allow you to set dependencies in a single
    place
    • Generate sub-Gemfiles for you
    • Install multiple versions of dependencies
    • Setup Bundler to use the correct version
    of dependency
    

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70. View Slide

71. Show that your gem is
    working with multiple
    versions of dependency
    

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72. .travis.yml:
    gemfile:
    - gemfiles/rails_3_1.gemfile
    - gemfiles/rails_3_2.gemfile
    

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75. View Slide

76. Remember
    

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77. View Slide

78. Test it against multiple
    versions of its dependencies
    

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79. Test it against multiple
    versions of its dependencies
    by using Appraisal x
    

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81. View Slide

82. RUBYKAIGI
    Promo code:
    $20 off first month of Prime
    http://learn.thoughtbot.com
    ͋Γ͕ͱ͏͍͟͝·͢ʂ
    

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