[RailsConf 2019] Terraforming legacy Rails applications

Video: https://www.youtube.com/watch?v=-NKpMn6XSjU
RailsConf: https://railsconf.com/program/sessions#session-832
GitHub: https://github.com/evilmartians/terraforming-rails

Rails has been around for (can you imagine!) about 15 years. Most Rails applications are no longer MVPs, but they grew from MVPs and usually contain a lot of legacy code that "just works."

And this legacy makes shipping new features harder and riskier: the new functionality have to co-exist with the code written years ago, and who knows what will blow up next?

I've been working on legacy codebases for the last few years, and I found turning legacy code into a legendary code to be a very exciting and challenging process.

I want to share the ideas and techniques I apply to make legacy codebases habitable and to prepare a breeding ground for the new features.

Transcript

1. TERRAFORMING
   LEGACY RAILS APPLICATIONS
   

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2. palkan_tula
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   2
   @palkan
   @palkan_tula
   Vladimir Dementyev
   933
   722
   406
   504
   

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3. palkan_tula
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   3
   evilmartians.com
   Brooklyn, NY
   Moscow, Russia
   

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5. palkan_tula
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   evl.ms/blog
   5
   

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6. palkan_tula
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   evilmartians.com
   6
   

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7. palkan_tula
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   FROM SCRATCH
   TWO TYPES OF PROJECTS
   7
   “Build us something cool!”
   SpaceX Star Hopper
   

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8. palkan_tula
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   FROM LEGACY
   TWO TYPES OF PROJECTS
   8
   “We’ve built something,
   make it cool!”
   Pepelats from Kin-dza-dza! (Soviet sci-fi)
   That’s my jam!
   

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9. palkan_tula
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   LEGACY
   9
   Jason Swett, RubyHACK 2019
   

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10. palkan_tula
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    10
    TEAM LEAD
    Evaluate project
    Make ready for
    others to join
    Prepare guidelines
    Captain Zelyonyy (Green),
    The Mystery of the third planet
    

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11. THIS TALK
    

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12. palkan_tula
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    #BoardGameGeek
    NOT ONLY A DEVELOPER
    

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13. palkan_tula
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    13
    TERRAFORMING
    MARS
    “Make Mars habitable!”
    Jacob Fryxelius, 2016
    

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14. palkan_tula
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    TERRAFORMING MARS
    14
    Corporations are competing to
    transform Mars into a habitable planet
    by raising temperature, creating a
    breathable atmosphere, and making
    oceans of water.
    As terraforming progresses, more and
    more people will immigrate from Earth
    to live on the Red Planet.
    

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15. palkan_tula
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    TERRAFORMING CODE
    15
    Engineers are transforming the legacy
    code into a habitable code by
    optimizing development process, adding
    confidence with tests and linters and
    creating a codeable atmosphere.
    As terraforming progresses, more and
    more people could join the project and
    work on new features.
    

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16. palkan_tula
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    16
    MARS
    LANDING
    Setting up the project
    PHASE #1
    

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17. palkan_tula
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    17
    GOAL
    PHASE #1
    “Developers should be able
    to run project
    with the least possible
    effort”
    

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18. palkan_tula
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    // Make running project locally as
    easy as running a few commands
    $ git clone project/repo.git
    $ cd repo
    $
    $ rails c
    Loading development environment
    2.6.2 (main):0>
    PHASE #1
    GOAL
    

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19. DEVELOPMENT
    ENVIRONMENT
    

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20. palkan_tula
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    “OLD SCHOOL” DEV ENV SETUP
    20
    Dev setup instructions from yet another Rails project
    

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21. palkan_tula
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    “NEW SCHOOL”
    21
    

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22. palkan_tula
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    DOCKER FOR DEV
    22
    Repeatable and predictable setup
    Always in sync
    

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23. palkan_tula
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    KEEPING ’N SYNC
    23
    

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24. palkan_tula
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    DOCKER FOR DEV
    24
    Repeatable and predictable setup
    Always in sync
    Painfully slow on Mac?
    

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25. palkan_tula
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    SLOW D4M
    25
    Use :cached folders
    Store assets/bundles in volumes
    Use NFS (if the first two are not enough)
    bit.ly/d4m-nfs
    

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26. palkan_tula
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    DOCKER FOR DEV
    26
    Repeatable and predictable setup
    Always in sync
    Painfully slow on Mac Windows
    "
    

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27. palkan_tula
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    # provision application
    $ dip provision
    # run web app
    $ dip rails s
    # simply launch bash within app directory
    $ dip bash
    # launch Postgres console
    $ dip psql
    BONUS: DIP
    27
    github.com/bibendi/dip
    

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28. palkan_tula
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    BONUS: DIP
    28
    # integrate with ZSH and
    # pretend you’re not using Docker at all :)
    $ dip console | source /dev/stdin
    # that runs the command within docker container…
    $ rails c
    # …but looks like you run it locally
    $ rspec spec/test_spec.rb:23
    github.com/bibendi/dip
    

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29. palkan_tula
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    READY
    TO LAUNCH?
    $ rails c
    ???
    

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30. palkan_tula
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    $ rails c
    Traceback (most recent call last):
    60: from bin/rails:9:in `'
    // 57 lines we don’t care about
    2: from /bundle/gems/activerecord-4.2.11.1/lib/
    active_record/connection_adapters/postgresql_adapter.rb:
    651:in `connect'
    1: from /bundle/gems/activerecord-4.2.11.1/lib/
    active_record/connection_adapters/postgresql_adapter.rb:
    651:in `new'
    /bundle/gems/activerecord-4.2.11.1/lib/active_record/
    connection_adapters/postgresql_adapter.rb:651:in
    `initialize': could not connect to server: No such file or
    directory (PG ::ConnectionBad)
    
    

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31. palkan_tula
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    $ rails c
    Traceback (most recent call last):
    60: from bin/rails:9:in `'
    // 56 lines we don’t care about
    3: from /bundle/gems/aws-sdk-core-2.10.9/lib/
    seahorse/client/base.rb:83:in `after_initialize'
    2: from /bundle/gems/aws-sdk-core-2.10.9/lib/
    seahorse/client/base.rb:83:in `each'
    1: from /bundle/gems/aws-sdk-core-2.10.9/lib/
    seahorse/client/base.rb:84:in `block in after_initialize'
    /bundle/gems/aws-sdk-core-2.10.9/lib/aws-sdk-core/plugins/
    regional_endpoint.rb:34:in `after_initialize': missing
    region; use :region option or export region name to
    ENV['AWS_REGION'] (Aws ::Errors ::MissingRegionError)
    
    

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32. palkan_tula
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    32
    WHY WE FAILED
    “The only host is
    localhost”
    Magic ENV
    Unexpected external
    deps
    Tha’s OK; Falcon 9 also failed
    

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33. CONFIGURATION
    

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34. palkan_tula
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    CONFIGURATION
    34
    Provide sensible defaults
    Minimize the number of external deps
    Organize configuration
    

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35. palkan_tula
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    SENSIBLE DEFAULTS
    35
    

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36. palkan_tula
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    Every required change could lead to
    “plz, help me” message in your Slack
    36
    

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37. palkan_tula
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    SENSIBLE DEFAULTS
    37
    # database.yml
    default: &default
    url: <%= ENV.fetch(“DATABASE_URL”, nil) %>
    # cable.yml
    default: &default
    adapter: redis
    url: <%= ENV.fetch(“REDIS_URL”, “localhost”) %>
    # docker-compose.yml
    services:
    app: &app
    environment:
    - REDIS_URL=redis: //redis:6379/
    - DATABASE_URL=postgres: //postgres:postgres@postgres:5432
    

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38. palkan_tula
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    OPTIONAL DEPS
    38
    # config/application.rb
    # Store uploaded files on the local file system
    # (unless AWS S3 is configured)
    config.active_storage.service =
    if AWSConfig.storage_configured?
    $stdout.puts "Using :amazon service for Active Storage"
    :amazon
    else
    :local
    end
    

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39. palkan_tula
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    OPTIONAL SERVICES
    39
    class TwilioNotifyClient
    def initialize(sid:)
    if sid.nil?
    @noop = true
    warn "Twilio Notify client initialized in the no-op mode.\n” \
    "See docs/twilio.md on how to configure it in development"
    return
    end
    end
    def send_notification(*args)
    return if noop?
    # ...
    end
    end
    TwilioNotifyClient.new(sid: ENV["TWILIO_NOTIFY_SID"])
    

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40. palkan_tula
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    CONFIGURATION
    40
    Provide sensible defaults
    Minimize the number of external deps
    Organize configuration
    

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41. palkan_tula
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    ENV HELL
    41
    ENV across all over the codebase
    Rails.env.smth? checks
    

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42. palkan_tula
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    ENV HELL
    42
    Limit ENV usage to config/environments/
    .rb
    Replace Rails.env.smth? with custom
    configuration settings
    

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43. palkan_tula
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    43
    # config/application.rb
    config.graphiql_enabled = false
    # config/development.rb
    config.graphiql_enabled = true
    # routes.rb
    - if Rails.env.development?
    + if Rails.application.config.graphiql_enabled
    mount Graphiql ::Rack.new, at: "/graphiql"
    end
    ENV HELL
    

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44. palkan_tula
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    LINT/ENV
    44
    bit.ly/lint-env-cop
    

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45. palkan_tula
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    ENV HELL
    45
    ENV across all over the codebase
    Rails.env.smth? checks
    .env with dozens of entries (and .env.sample
    is out-of-date)
    

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46. palkan_tula
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    ENV HELL
    46
    

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47. palkan_tula
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    ENV HELL
    47
    
    

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48. palkan_tula
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    HEROKU HELL
    48
    $ heroku config -a legacy-project | wc -l
    131
    

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49. NEW WORLD?
    

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50. palkan_tula
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    KEEPING CONFIGS
    50
    Store sensitive information in Rails Credentials
    (or similar)
    Keep non-sensitive information in named YAML
    files
    Allow overriding via ENV
    

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51. palkan_tula
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    RAILS 6 CREDENTIALS
    51
    

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52. palkan_tula
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    KEEPING CONFIGS
    52
    github.com/palkan/anyway_config
    

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53. palkan_tula
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    KEEPING CONFIGS
    53
    github.com/palkan/anyway_config
    

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54. palkan_tula
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    54
    PHASE #1
    * We’re on Mars!
    MARS LANDING
    ✅ Repeatable dev
    env setup
    ✅ Transparent and
    zero-“changeme”
    configuration
    

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55. palkan_tula
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    55
    BREATHABLE
    ATMOSPHERE
    Raising tests
    reliability level
    PHASE #2
    

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56. palkan_tula
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    TESTS ~ OXYGEN
    56
    Developing without tests is like breathing with
    no air
    Developing with slow tests is like breathing on
    the top of mt. Jomolungma
    Developing with unreliable (flaky) tests is like
    breathing in Chelyabinsk
    

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57. CHELYABINSK
    

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58. CHELYABINSK
    

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59. palkan_tula
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    59
    GOAL
    PHASE #2
    “Tests should be reliable
    and fast to not block
    the development”
    * Make oxygen level at least 21% to 2065!
    

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60. palkan_tula
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    BREATHABLE TESTS
    60
    Improve test suite speed
    

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61. RAISE YOUR HAND
    IF YOUR TESTS ARE SLOW
    

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62. palkan_tula
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    github.com/palkan/test-prof
    TestProf
    62
    test-prof.evilmartians.io
    

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63. palkan_tula
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    TestProf
    63
    Tests specific profilers
    RSpec / Minitest extensions to speed up tests
    with as little refactoring as possible
    Custom Rubocop cops
    

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64. palkan_tula
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    64
    3700 tests / 22 minutes = 170 TPM
    9800 tests / 14 minutes = 700 TPM
    4x faster!
    TestProf
    Born in “production”
    

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65. palkan_tula
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    HOW DID WE GET THERE?
    65
    

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66. palkan_tula
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    99 PROBLEMS OF SLOW TESTS
    66
    bit.ly/test-prof-paris
    

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67. palkan_tula
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    FASTER TESTS: HIGHLIGHTS
    67
    Get rid of database_cleaner
    

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68. palkan_tula
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    RAILS 5.1
    68
    github.com/rails/rails/pull/28083
    

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69. palkan_tula
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    ActiveRecordSharedConnection
    69
    test-prof.evilmartians.io/#/active_record_shared_connection
    # Rails 5.1+
    # connection is shared out-of-the-box
    # Rails <5.1
    require “test_prof/recipes/active_record_one_love"
    

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70. palkan_tula
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    FASTER TESTS: HIGHLIGHTS
    70
    Get rid of database_cleaner
    Do not inline background jobs by default
    

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71. palkan_tula
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    SIDEKIQ SHAME
    71
    gist.github.com/nateberkopec/3932fce995c9feddd411417fc9bf33bf
    

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72. palkan_tula
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    SIDEKIQ SHAME
    72
    shared_context "sq:inline" do
    around(:each) do |ex|
    Sidekiq ::Testing.inline!(&ex)
    end
    end
    RSpec.configure do |config|
    config.include_context "sq:inline", sidekiq: :inline
    end
    

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73. palkan_tula
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    SIDEKIQ SHAME
    73
    evl.ms/blog
    

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74. palkan_tula
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    FASTER TESTS: HIGHLIGHTS
    74
    You (likely) don’t need database_cleaner
    Do not inline background jobs by default
    Take care of your factories
    

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75. palkan_tula
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    FACTORY CASCADE
    75
    factory :comment do
    answer
    author
    end
    factory :answer do
    question
    author
    end
    factory :question do
    author
    end
    create(:comment) # => creates 5 records
    

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76. palkan_tula
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    FACTORY THERAPY
    76
    evl.ms/blog
    

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77. palkan_tula
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    FASTER TESTS: HIGHLIGHTS
    77
    You (likely) don’t need database_cleaner
    Do not inline background jobs by default
    Take care of your factories
    …more
    

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78. palkan_tula
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    test-prof.evilmartians.io
    78
    

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79. palkan_tula
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    79
    Improve test suite speed
    Remove/reduce flakiness
    BREATHABLE TESTS
    

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80. palkan_tula
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    FIXING FLAKY TESTS
    80
    

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81. palkan_tula
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    81
    FIGHTING THE FLAKINESS
    bit.ly/flaky-fight
    

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82. palkan_tula
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    FACTORY LINTER
    82
    // Check factory definitions
    $ bundle exec rake factory_lint
    Factory lint detected the following errors:
    - :city should use a sequence for :name attribute, 'cause it has a
    uniqueness constraint
    bit.ly/factory-lint
    

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83. palkan_tula
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    FACTORY LINTER
    83
    # city.rb
    FactoryBot.define do
    factory :city do
    - name { Faker ::Address.city }
    + sequence(:name) { |n| Faker ::Address.city + " ( #{n})" }
    end
    end
    bit.ly/factory-lint
    

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84. palkan_tula
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    84
    PHASE #2
    BREATHABLE
    ATMOSPHERE
    ✅ Tests do not block
    the development
    

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85. binding.cat
    

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86. palkan_tula
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    86
    TURN ICE
    INTO WATER
    Bring project back to
    the healthy state
    PHASE #3
    * Korolev crater
    

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87. palkan_tula
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    87
    GOAL
    PHASE #3
    “Project shouldn’t have
    significant security,
    consistency and
    performance issues“
    

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88. palkan_tula
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    SECURITY
    88
    Check dependencies (bundler-audit)
    

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89. palkan_tula
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    bundler-audit
    89
    $ bundle audit update && bundle audit check
    Name: nokogiri
    Version: 1.8.5
    Advisory: CVE-2019-11068
    Criticality: Unknown
    URL: https: //github.com/sparklemotion/nokogiri/issues/1892
    Title: Nokogiri gem, via libxslt, is affected by improper access control
    vulnerability
    Solution: upgrade to >= 1.10.3
    Vulnerabilities found!
    github.com/rubysec/bundler-audit
    

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90. palkan_tula
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    SECURITY
    90
    Check dependencies (bundler-audit)
    Check application code (brakeman, rubocop)
    

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91. palkan_tula
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    BRAKEMAN
    91
    brakemanscanner.org
    

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92. palkan_tula
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    RUBOCOP SECURITY
    92
    // Check potentially insecure code
    $ bundle exec rubocop --only Security
    Offenses:
    script.rb:33:21: C: Security/JSONLoad: Prefer JSON.parse over JSON.load.
    data = JSON.load(input.meta)
    ^^^^
    

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93. palkan_tula
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    CONSISTENCY
    93
    Models vs. DB
    user.update!(params.require(:user).permit(:name))
    => PG ::StringDataRightTruncation: ERROR: value too long for
    type character varying(255)
    
    

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94. palkan_tula
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    database_consistency
    94
    github.com/djezzl/database_consistency
    

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95. palkan_tula
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    95
    class Topic < ActiveRecord ::Base
    validates :description, presence: true
    end
    $ bundle exec database_consistency
    // description column is missing `null: false` constraint
    fail Topic description column should be required in the database
    database_consistency
    github.com/djezzl/database_consistency
    

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96. palkan_tula
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    database_validations
    96
    github.com/toptal/database_validations
    class Home < ActiveRecord ::Base
    # checks that a foreign key present
    db_belongs_to :city
    # checks that a unique index is present
    validates_db_uniqueness_of :name, case_sensitive: false
    end
    

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97. palkan_tula
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    CONSISTENCY
    97
    Models vs. DB
    Code style?
    

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98. palkan_tula
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    RUBOCOP
    98
    Strict config
    

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99. palkan_tula
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    .rubocop_strict.yml
    99
    AllCops:
    DisabledByDefault: true
    Security:
    Enabled: true
    Lint/Debugger:
    Enabled: true
    Lint/Syntax:
    Enabled: true
    Lint/Env:
    Enabled: true
    RSpec/Focus:
    Enabled: true
    

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100. palkan_tula
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     .rubocop_strict.yml
     100
     AllCops:
     DisabledByDefault: true
     Security:
     Enabled: true
     Lint/Debugger:
     Enabled: true
     Lint/Syntax:
     Enabled: true
     Lint/Env:
     Enabled: true
     RSpec/Focus:
     Enabled: true
     

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101. palkan_tula
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     .rubocop_strict.yml
     101
     AllCops:
     DisabledByDefault: true
     Security:
     Enabled: true
     Lint/Debugger:
     Enabled: true
     Lint/Syntax:
     Enabled: true
     Lint/Env:
     Enabled: true
     RSpec/Focus:
     Enabled: true
     

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102. palkan_tula
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     .rubocop_strict.yml
     102
     AllCops:
     DisabledByDefault: true
     Security:
     Enabled: true
     Lint/Debugger:
     Enabled: true
     Lint/Syntax:
     Enabled: true
     Lint/Env:
     Enabled: true
     RSpec/Focus:
     Enabled: true
     

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103. palkan_tula
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     .rubocop_strict.yml
     103
     AllCops:
     DisabledByDefault: true
     Security:
     Enabled: true
     Lint/Debugger:
     Enabled: true
     Lint/Syntax:
     Enabled: true
     Lint/Env:
     Enabled: true
     RSpec/Focus:
     Enabled: true
     

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104. palkan_tula
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     .rubocop_strict.yml + CI
     104
     # .circleci/config.yml
     rubocop_strict:
     executor: ruby
     steps:
     - attach_workspace:
     at: .
     - run:
     name: Strict Rubocop check
     command: |
     bundle exec rubocop -c .rubocop_strict.yml
     

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105. palkan_tula
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     RUBOCOP
     105
     Strict config
     Progressive enhancement
     

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106. palkan_tula
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     .rubocop.yml
     106
     require:
     - rubocop-rspec
     - standard/cop/semantic_blocks
     inherit_gem:
     standard: config/base.yml
     AllCops:
     Include:
     # explicitly specify terraformed code
     - "**/community/**/*.rb"
     Exclude:
     - "db/schema.rb"
     - "bin /*"
     

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107. palkan_tula
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     .rubocop.yml
     107
     require:
     - rubocop-rspec
     - standard/cop/semantic_blocks
     inherit_gem:
     standard: config/base.yml
     AllCops:
     Include:
     # explicitly specify terraformed code
     - "**/community/**/*.rb"
     Exclude:
     - "db/schema.rb"
     - "bin /*"
     

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108. palkan_tula
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     .rubocop.yml
     108
     require:
     - rubocop-rspec
     - standard/cop/semantic_blocks
     inherit_gem:
     standard: config/base.yml
     AllCops:
     Include:
     # explicitly specify terraformed code
     - "**/community/**/*.rb"
     Exclude:
     - "db/schema.rb"
     - "bin /*"
     

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109. palkan_tula
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     STANDARD
     109
     github.com/testdouble/standard
     

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110. palkan_tula
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     110
     SIDE
     EFFECTS
     

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111. palkan_tula
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     SIDE EFFECTS
     111
     Non-atomic transactions
     class Post < ActiveRecord ::Base
     after_create :notify_author
     def notify_users
     # send email even if transaction failed
     UsersMailer.new_post(author, post.title).deliver_later
     end
     end
     

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112. palkan_tula
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     ISOLATOR
     112
     github.com/palkan/isolator
     

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113. palkan_tula
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     ISOLATOR
     113
     github.com/palkan/isolator
     $ bundle exec rspec
     1) Create post example
     Failure/Error: job_or_instantiate(*args).enqueue
     Isolator ::BackgroundJobError:
     You are trying to enqueue background job inside db transaction.
     Details: ActionMailer ::DeliveryJob (UsersMailer, new_post)
     

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114. palkan_tula
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     114
     DEAD
     CODE
     

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115. palkan_tula
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     DEAD CODE
     115
     Gems
     

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116. palkan_tula
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     DEAD GEMS
     116
     $ GEM_TRACK=1 bundle exec rspec
     Maybe unused gems:
     activerecord-postgres_enum-0.3.0
     avatax-18.12.0
     aws-sdk-2.10.9
     rails-4.2.11.1
     gibbon-2.2.5
     bit.ly/track-gems
     

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117. palkan_tula
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     117
     Gems
     Routes/controllers
     DEAD CODE
     

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118. palkan_tula
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     traceroute
     118
     github.com/amatsuda/traceroute
     $ bundle exec rake traceroute
     Unused routes (3):
     users#create
     users#new
     catalog#purchase
     Unreachable action methods (1):
     users#index2
     

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119. palkan_tula
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     119
     Gems
     Routes/controllers
     Views
     DEAD CODE
     

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120. palkan_tula
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     TEMPLATES TRACKER
     120
     $ TT=1 bundle exec rspec
     ======== Unused Templates =========
     /app/app/views/home/index.html.erb
     /app/app/views/housekeeping/scheduling/index.html.erb
     bit.ly/track-templates
     

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121. palkan_tula
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     121
     Gems
     Routes/controllers
     Views
     Factories NEW!
     DEAD CODE
     

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122. palkan_tula
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     FACTORY TRACE
     122
     $ FB_TRACE=1 bundle exec rspec
     total number of unique used factories & traits: 1
     total number of unique unused factories & traits: 3
     unused trait 'with_phone' of factory 'user'
     unused factory 'special_user'
     unused global trait 'with_email'
     github.com/djezzzl/factory_trace
     

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123. palkan_tula
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     123
     TURN ICE
     INTO WATER
     PHASE #3
     ✅ Project is healthy
     enough to bring more
     people
     

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124. palkan_tula
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     124
     ROBOTS
     Automating things
     BONUS
     

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125. palkan_tula
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     LEFT HOOK
     125
     github.com/Arkweid/lefthook
     $ git commit -m "chore: use lefthook"
     RUNNING HOOKS GROUP: pre-commit
     EXECUTE > rubocop
     1 file inspected, 1 offense detected
     rubocop
     

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126. palkan_tula
     palkan RailsConf 2019
     LEFT HOOK
     126
     github.com/Arkweid/lefthook
     $ git commit -m "chore: use lefthook"
     RUNNING HOOKS GROUP: pre-commit
     EXECUTE > rubocop
     1 file inspected, no offenses detected
     ✅ rubocop
     RUNNING HOOKS GROUP: prepare-commit-msg
     EXECUTE > jira_link.rb
     JIRA ticket ID (type 'N/n' to skip): 2019
     ✅ jira_link.rb
     

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127. palkan_tula
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     DANGER
     127
     danger.systems
     

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128. palkan_tula
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     FINAL
     SCORING
     128
     

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129. palkan_tula
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     github.com/evilmartians/terraforming-rails
     DO IT YOURSELF
     129
     

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130. palkan_tula
     palkan RailsConf 2019
     …OR NOT
     130
     evilmartians.com
     

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131. COMING SOON
     

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132. SPECIAL THANKS
     2061.su
     

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133. palkan_tula
     palkan RailsConf 2019
     133
     THANK YOU!
     Vladimir Dementyev
     evilmartians.com
     @evilmartians
     

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