A Guided Read of Minitest

Why is Minitest so much shorter than RSpec? What does Minitest's size tell us about it's philosophy on testing (and Ruby)?

Transcript

1. MINITEST
   A PHILOSOPHY OF PAIN
   Exploring testing philosophy through code-reading
   with @nateberkopec
   @nateberkopec
   

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2. I'm @nateberkopec.
   I write about Ruby
   performance at
   nateberkopec.com.
   @nateberkopec
   

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3. Quick Survey
   @nateberkopec
   

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4. @nateberkopec
   

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5. def object_under_test.stub
   true
   end
   @nateberkopec
   

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6. Pain lead me to learning
   something new about
   Ruby.
   @nateberkopec
   

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7. The elephant
   in the room:
   RSpec
   @nateberkopec
   

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8. @nateberkopec
   

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9. I'm a Minitest
   guy.
   @nateberkopec
   

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10. This talk is about the
    philosophy of Minitest
    revealed through code.
    @nateberkopec
    

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11. Minitest is
    reactionary
    @nateberkopec
    

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12. History
    Lesson
    @nateberkopec
    

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13. 90 lines
    http://tinyurl.com/
    originalminitest
    @nateberkopec
    

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14. Replacement
    for test/unit
    @nateberkopec
    

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15. A code
    reader's best
    friend: cloc
    @nateberkopec
    

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16. Minitest
    Comments + README: 1699 lines.
    Ruby code: 1604 lines.
    @nateberkopec
    

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17. Rspec has 4 major components:
    → rspec-core
    → rspec-expectations
    → rspec-mocks
    → rspec-support
    @nateberkopec
    

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18. → rspec-core: 6672 lines
    → rspec-expectations: 3672 lines
    → rspec-mocks: 3930 lines
    → rspec-support: 1569 lines
    Total: 15843 Lines
    @nateberkopec
    

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19. Minitest is 1/10th the size
    of RSpec in total.
    @nateberkopec
    

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20. If Minitest is The Mouse
    and The Motorcycle
    (22,416 words)...
    @nateberkopec
    

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21. ...RSpec is Ulysses by
    James Joyce (265,000
    words).
    @nateberkopec
    

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22. Do Less With
    Less
    @nateberkopec
    

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23. RSpec includes 1639 lines of formatters!
    (HTML, JSON, the progress bar, etc)
    @nateberkopec
    

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24. @nateberkopec
    

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25. rspec-mocks is 28 times
    larger than minitest/mock
    @nateberkopec
    

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26. Statism is good.
    @nateberkopec
    

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27. "A stateist tester asserts that a method returns a
    particular value. A mockist tester asserts that a
    method triggers a specific set of interactions with
    the object's dependencies."
    - James Golick
    @nateberkopec
    

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28. @nateberkopec
    

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29. The largest file in RSpec
    is configuration.rb
    758 lines
    @nateberkopec
    

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30. The largest file in
    Minitest is minitest.rb
    446 lines
    @nateberkopec
    

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31. Minitest knows whats
    best for you
    @nateberkopec
    

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32. @nateberkopec
    

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33. @nateberkopec
    

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34. # test.rb
    require 'minitest/autorun'
    class MyTest < Minitest::Test
    def test_the_truth
    assert_equal 1, 1
    end
    end
    @nateberkopec
    

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35. $ ruby test.rb
    Run options: --seed 20624
    # Running:
    .
    Finished in 0.001794s, 557.4841 runs/s, 557.4841 assertions/s.
    1 runs, 1 assertions, 0 failures, 0 errors, 0 skips
    @nateberkopec
    

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36. # test.rb
    require 'minitest/autorun'
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37. # minitest/autorun.rb
    require "minitest" # requires minitest/test
    require "minitest/spec" # requires minitest/expectations
    require "minitest/mock"
    Minitest.autorun
    @nateberkopec
    

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38. # minitest.rb
    module Minitest
    # ... snip ...
    def self.autorun
    at_exit {
    next if $! and not ($!.kind_of? SystemExit and $!.success?)
    exit_code = nil
    at_exit {
    @@after_run.reverse_each(&:call)
    exit exit_code || false
    }
    exit_code = Minitest.run ARGV
    } unless @@installed_at_exit
    @@installed_at_exit = true
    end
    end
    @nateberkopec
    

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39. def self.autorun
    if autorun_disabled?
    RSpec.deprecate("Requiring `rspec/autorun` when running RSpec via the `rspec` command")
    return
    elsif installed_at_exit? || running_in_drb?
    return
    end
    at_exit { perform_at_exit }
    @installed_at_exit = true
    end
    def self.perform_at_exit
    return unless $!.nil? || $!.is_a?(SystemExit)
    invoke
    end
    def self.invoke
    disable_autorun!
    status = run(ARGV, $stderr, $stdout).to_i
    exit(status) if status != 0
    end
    def self.disable_autorun!
    @autorun_disabled = true
    end
    def self.installed_at_exit?
    @installed_at_exit ||= false
    end
    @nateberkopec
    

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40. # RSpec
    def self.installed_at_exit?
    @installed_at_exit ||= false
    end
    # Minitest
    @@installed_at_exit = true
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41. Do the Simplest Thing
    That Could Posibly Work
    @nateberkopec
    

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42. # Minitest.autorun -> Minitest.run
    def self.run reporter, options = {}
    filter = options[:filter] || "/./"
    filter = Regexp.new $1 if filter =~ %r%/(.*)/%
    filtered_methods = self.runnable_methods.find_all { |m|
    filter === m || filter === "#{self}##{m}"
    }
    return if filtered_methods.empty?
    with_info_handler reporter do
    filtered_methods.each do |method_name|
    run_one_method self, method_name, reporter
    end
    end
    end
    @nateberkopec
    

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43. def self.run reporter, options = {}
    def self.run(reporter, options = {})
    def some_method arg1 arg2 arg3
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44. puts array.delete hash.fetch :foo
    via David Brady
    @nateberkopec
    

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45. puts array.delete(hash.fetch(:foo))
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46. thing_i_want_to_remove = hash.fetch :foo
    array.delete thing_i_want_to_remove
    puts thing_i_want_to_remove
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47. Pain is good. Pain is
    signal.
    @nateberkopec
    

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48. Test
    Discovery?
    @nateberkopec
    

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49. # minitest.rb
    module Minitest
    class Runnable # Minitest::Test is a Runnable
    def self.runnables
    @@runnables
    end
    def self.inherited klass # :nodoc:
    self.runnables << klass
    super
    end
    end
    end
    @nateberkopec
    

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50. class Foo
    def self.inherited(subclass)
    puts "New subclass: #{subclass}"
    end
    end
    @nateberkopec
    

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51. # test.rb
    require 'minitest/autorun'
    class MyTest < Minitest::Test
    def test_the_truth
    assert_equal 1, 1
    end
    end
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52. Stdlib used in Minitest
    → OptionParser
    → Thread
    → Mutex
    → StringIO
    → Tempfile
    @nateberkopec
    

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53. Core/stdlib classes RSpec overrides or re-
    implements
    → Set
    → flat_map
    → Thread local variables
    → rand (!!!)
    @nateberkopec
    

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54. Use what is given.
    @nateberkopec
    

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55. Defining Tests
    in Minitest
    @nateberkopec
    

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56. # Minitest::Test
    # This was called in Minitest.run
    def self.runnable_methods
    methods = methods_matching(/^test_/) #one-liner that returns a list of methods as strings
    case self.test_order
    when :random, :parallel then
    max = methods.size
    methods.sort.sort_by { rand max }
    when :alpha, :sorted then
    methods.sort
    else
    raise "Unknown test_order: #{self.test_order.inspect}"
    end
    end
    @nateberkopec
    

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57. define_example_method :example
    define_example_method :it
    define_example_method :specify
    define_example_method :focus, :focus => true
    define_example_method :fexample, :focus => true
    define_example_method :fit, :focus => true
    define_example_method :fspecify, :focus => true
    define_example_method :xexample, :skip => 'Temporarily skipped with xexample'
    define_example_method :xit, :skip => 'Temporarily skipped with xit'
    define_example_method :xspecify, :skip => 'Temporarily skipped with xspecify'
    define_example_method :skip, :skip => true
    define_example_method :pending, :pending => true
    @nateberkopec
    

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58. def self.define_example_method(name, extra_options={})
    idempotently_define_singleton_method(name) do |*all_args, &block|
    desc, *args = *all_args
    options = Metadata.build_hash_from(args)
    options.update(:skip => RSpec::Core::Pending::NOT_YET_IMPLEMENTED) unless block
    options.update(extra_options)
    example = RSpec::Core::Example.new(self, desc, options, block)
    examples << example
    example
    end
    end
    @nateberkopec
    

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59. Reduce the API surface
    @nateberkopec
    

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60. def assert_includes collection, obj, msg = nil
    msg = message(msg) {
    "Expected #{mu_pp(collection)} to include #{mu_pp(obj)}"
    }
    assert_respond_to collection, :include?
    assert collection.include?(obj), msg
    end
    @nateberkopec
    

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61. def assert test, msg = nil
    self.assertions += 1
    unless test then
    msg ||= "Failed assertion, no message given."
    msg = msg.call if Proc === msg
    raise Minitest::Assertion, msg
    end
    true
    end
    @nateberkopec
    

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62. module Minitest
    module Test
    include Assertions
    end
    end
    @nateberkopec
    

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63. Rspec: I honestly have no
    idea
    @nateberkopec
    

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64. RSpec::Matchers.define :be_a_multiple_of do |expected|
    match do |actual|
    actual % expected == 0
    end
    end
    @nateberkopec
    

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65. Abstraction is the Enemy
    @nateberkopec
    

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66. A philosophy
    of pain
    @nateberkopec
    

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67. MINITEST
    A PHILOSOPHY OF PAIN
    Slides
    @nateberkopec
    

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68. Secrets
    verbose mode
    self.makemydiffs_pretty!
    @nateberkopec
    

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69. Other things that don't exist
    → stubs (singletons, Liskov Substitution (TestClass
    versions))
    → assertnothingraised
    → a minitest runner
    @nateberkopec
    

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70. @nateberkopec
    

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