RSpec: It Isn't Actually Magic

Transcript

1. Follow along at: http://bit.ly/rspec_magic
2. Everybody loves RSpec
6. March, 2011
7. RSpec is complicated
8. While I think the benefits are discernable…
9. This is mostly about the complicated
10. Why is RSpec complicated? •RSpec is expressive •And very flexible •And it’s a big library
11. How flexible is RSpec?
12. With about 10 lines of configuration
13. This flexible… RSpec.! Hotel do
 " "works" do
 #(1 + 1).to ❤(2)
 end
 end
14. RSpec: It’s not actually Magic Noel Rappin Table XI
15. We’re going to look at RSpec source code
16. Please don’t avert your eyes
17. Why talk about RSpec internals?
18. Talks should tell a story
19. Once upon a time, there was a test… require 'rails_helper'
 
 RSpec.describe Name do
 it "produces a sort name" do
 name = Name.new("Noel", "Rappin")
 expect(name.sort_name).to eq("Rappin, Noel")
 end
 end
20. RSpec with Parentheses require 'rails_helper'
 
 RSpec.describe(Name) do
 self.it(“produces a sort name”) do
 name = Name.new("Noel", "Rappin")
 self.expect(name.sort_name).to(self.eq(“Rappin, Noel”))
 end
 end
21. Key RSpec words require 'rails_helper'
 
 RSpec.describe(Name) do
 self.it(“produces a sort name”) do
 name = Name.new("Noel", "Rappin")
 self.expect(name.sort_name).to(self.eq(“Rappin, Noel”))
 end
 end
22. RSpec power words describe it expect to(something)
23. RSpec power words describe it expect to(something) ExampleGroup Example ExpectationTarget Matcher
24. require 'rails_helper'
 
 RSpec.describe(Name) do
 self.it(“produces a sort name”) do
 name = Name.new("Noel", "Rappin")
 self.expect(name.sort_name).to(self.eq(“Rappin, Noel”))
 end
 end
25. require 'rails_helper'
 
 RSpec.describe(Name) do
 self.it(“produces a sort name”) do
 name = Name.new("Noel", "Rappin")
 self.expect(name.sort_name).to(self.eq(“Rappin, Noel”))
 end
 end Example Group
26. require 'rails_helper'
 
 RSpec.describe(Name) do
 self.it(“produces a sort name”) do
 name = Name.new("Noel", "Rappin")
 self.expect(name.sort_name).to(self.eq(“Rappin, Noel”))
 end
 end Example Group Example
27. require 'rails_helper'
 
 RSpec.describe(Name) do
 self.it(“produces a sort name”) do
 name = Name.new("Noel", "Rappin")
 self.expect(name.sort_name).to(self.eq(“Rappin, Noel”))
 end
 end Example Group Example ExpectationTarget
28. require 'rails_helper'
 
 RSpec.describe(Name) do
 self.it(“produces a sort name”) do
 name = Name.new("Noel", "Rappin")
 self.expect(name.sort_name).to(self.eq(“Rappin, Noel”))
 end
 end Example Group Example ExpectationTarget Matcher
29. Example Group • Created by describe or context • Arguments are a description, metadata, and block • Creates an anonymous subclass of ExampleGroup • Executes the block in the context of the class RSpec.describe Name, metadata: true do
 #stuff
 end
30. Creating an ExampleGroup def self.subclass(parent, description, args, &example_group_block)
 subclass = Class.new(parent)
 subclass.set_it_up(description, *args, &example_group_block)
 subclass.module_exec(&example_group_block) if example_group_block
 MemoizedHelpers.define_helpers_on(subclass)
 subclass
 end
31. Example Group Subclass def self.subclass(parent, description, args, &example_group_block)
 subclass = Class.new(parent)
 subclass.set_it_up(description, *args, &example_group_block)
 subclass.module_exec(&example_group_block) if example_group_block
 MemoizedHelpers.define_helpers_on(subclass)
 subclass
 end
32. Setup (configure mock package) def self.subclass(parent, description, args, &example_group_block)
 subclass = Class.new(parent)
 subclass.set_it_up(description, *args, &example_group_block)
 subclass.module_exec(&example_group_block) if example_group_block
 MemoizedHelpers.define_helpers_on(subclass)
 subclass
 end
33. Setup (configure mock package) def self.subclass(parent, description, args, &example_group_block)
 subclass = Class.new(parent)
 subclass.set_it_up(description, *args, &example_group_block)
 subclass.module_exec(&example_group_block) if example_group_block
 MemoizedHelpers.define_helpers_on(subclass)
 subclass
 end
34. Setup (configure mock package) def self.subclass(parent, description, args, &example_group_block)
 subclass = Class.new(parent)
 subclass.set_it_up(description, *args, &example_group_block)
 subclass.module_exec(&example_group_block) if example_group_block
 MemoizedHelpers.define_helpers_on(subclass)
 subclass
 end
35. What is module_exec? class Thing
 end
 
 Thing.module_exec(arg) do |arg|
 def hello() "Hello there!" end
 end 
 puts Thing.new.hello()
36. Minimal RSpec with Parentheses require 'rails_helper'
 
 <<ExampleGroupSubclass>>.module_exec do
 it(“produces a sort name”) do
 name = Name.new("Noel", "Rappin")
 expect(name.sort_name).to(eq(“Rappin, Noel”))
 end
 end
37. Example • Created by it, example, specify — instance methods of ExampleGroup • Arguments are description, metadata, and a block • Assigns the example to an array class attribute of the ExampleGroup it(“produces a sort name”) do
 #stuff
 end
38. Creating an Example desc, *args = *all_args
 options = Metadata.build_hash_from(args) unless block
 options.update(:skip => RSpec::Core::Pending::NOT_YET_IMPLEMENTED) end options.update(extra_options)
 examples << RSpec::Core::Example.new(self, desc, options, block)
 examples.last
39. Creating an Example desc, *args = *all_args
 options = Metadata.build_hash_from(args) unless block
 options.update(:skip => RSpec::Core::Pending::NOT_YET_IMPLEMENTED) end options.update(extra_options)
 examples << RSpec::Core::Example.new(self, desc, options, block)
 examples.last
40. Creating an Example desc, *args = *all_args
 options = Metadata.build_hash_from(args) unless block
 options.update(:skip => RSpec::Core::Pending::NOT_YET_IMPLEMENTED) end options.update(extra_options)
 examples << RSpec::Core::Example.new(self, desc, options, block)
 examples.last
41. What happens at run time? •RSpec creates an instance of the anonymous ExampleGroup class •The new instance runs all of its examples
42. Running ExampleGroup runs examples ExampleGroup runs each example Example runs
43. Running an Example Group def self.run(reporter=RSpec::Core::NullReporter)
 return if RSpec.world.wants_to_quit
 reporter.example_group_started(self)
 should_run_context_hooks = descendant_filtered_examples.any?
 begin
 run_before_context_hooks(new('before(:context) hook')) if should_run_context_hooks
 result_for_this_group = run_examples(reporter)
 results_for_descendants = ordering_strategy.order(children).map { |child| child.run(reporter) }.all?
 result_for_this_group && results_for_descendants
 rescue Pending::SkipDeclaredInExample => ex
 for_filtered_examples(reporter) { |example| example.skip_with_exception(reporter, ex) }
 true
 rescue Exception => ex
 RSpec.world.wants_to_quit = true if fail_fast?
 for_filtered_examples(reporter) { |example| example.fail_with_exception(reporter, ex) }
 false
 ensure
 run_after_context_hooks(new('after(:context) hook')) if should_run_context_hooks
 reporter.example_group_finished(self)
 end
 end
44. Running an Example Group def self.run(reporter=RSpec::Core::NullReporter)
 return if RSpec.world.wants_to_quit
 reporter.example_group_started(self)
 should_run_context_hooks = descendant_filtered_examples.any?

45. Running an Example Group begin
 run_before_context_hooks(new('before(:context) hook')) if should_run_context_hooks
 result_for_this_group = run_examples(reporter)
 results_for_descendants = ordering_strategy.order(children).map { |child| child.run(reporter) }.all?
 result_for_this_group && results_for_descendants

46. Running an Example Group 
 rescue Pending::SkipDeclaredInExample => ex
 for_filtered_examples(reporter) { |example| example.skip_with_exception(reporter, ex) }
 true
 rescue Exception => ex
 RSpec.world.wants_to_quit = true if fail_fast?
 for_filtered_examples(reporter) { |example| example.fail_with_exception(reporter, ex) }
 false

47. Running an Example Group 
 ensure
 run_after_context_hooks(new('after(:context) hook')) if should_run_context_hooks
 reporter.example_group_finished(self)
 end
 end
48. Running an Example Group def self.run(reporter=RSpec::Core::NullReporter)
 return if RSpec.world.wants_to_quit
 reporter.example_group_started(self)
 should_run_context_hooks = descendant_filtered_examples.any?
 begin
 run_before_context_hooks(new('before(:context) hook')) if should_run_context_hooks
 result_for_this_group = run_examples(reporter)
 results_for_descendants = ordering_strategy.order(children).map { |child| child.run(reporter) }.all?
 result_for_this_group && results_for_descendants
 rescue Pending::SkipDeclaredInExample => ex
 for_filtered_examples(reporter) { |example| example.skip_with_exception(reporter, ex) }
 true
 rescue Exception => ex
 RSpec.world.wants_to_quit = true if fail_fast?
 for_filtered_examples(reporter) { |example| example.fail_with_exception(reporter, ex) }
 false
 ensure
 run_after_context_hooks(new('after(:context) hook')) if should_run_context_hooks
 reporter.example_group_finished(self)
 end
 end
49. Running Examples def self.run_examples(reporter)
 ordering_strategy.order(filtered_examples).map do |example|
 next if RSpec.world.wants_to_quit
 instance = new(example.inspect_output)
 set_ivars(instance, before_context_ivars)
 succeeded = example.run(instance, reporter)
 RSpec.world.wants_to_quit = true if fail_fast? && !succeeded
 succeeded
 end.all?
 end
50. Running Examples def self.run_examples(reporter)
 ordering_strategy.order(filtered_examples).map do |example|
 next if RSpec.world.wants_to_quit
 instance = new(example.inspect_output)
 set_ivars(instance, before_context_ivars)
 succeeded = example.run(instance, reporter)
 RSpec.world.wants_to_quit = true if fail_fast? && !succeeded
 succeeded
 end.all?
 end
51. Running Examples def self.run_examples(reporter)
 ordering_strategy.order(filtered_examples).map do |example|
 next if RSpec.world.wants_to_quit
 instance = new(example.inspect_output)
 set_ivars(instance, before_context_ivars)
 succeeded = example.run(instance, reporter)
 RSpec.world.wants_to_quit = true if fail_fast? && !succeeded
 succeeded
 end.all?
 end
52. Running Examples def self.run_examples(reporter)
 ordering_strategy.order(filtered_examples).map do |example|
 next if RSpec.world.wants_to_quit
 instance = new(example.inspect_output)
 set_ivars(instance, before_context_ivars)
 succeeded = example.run(instance, reporter)
 RSpec.world.wants_to_quit = true if fail_fast? && !succeeded
 succeeded
 end.all?
 end
53. Running Examples def self.run_examples(reporter)
 ordering_strategy.order(filtered_examples).map do |example|
 next if RSpec.world.wants_to_quit
 instance = new(example.inspect_output)
 set_ivars(instance, before_context_ivars)
 succeeded = example.run(instance, reporter)
 RSpec.world.wants_to_quit = true if fail_fast? && !succeeded
 succeeded
 end.all?
 end
54. Running Examples def self.run_examples(reporter)
 ordering_strategy.order(filtered_examples).map do |example|
 next if RSpec.world.wants_to_quit
 instance = new(example.inspect_output)
 set_ivars(instance, before_context_ivars)
 succeeded = example.run(instance, reporter)
 RSpec.world.wants_to_quit = true if fail_fast? && !succeeded
 succeeded
 end.all?
 end
55. Running Examples def self.run_examples(reporter)
 ordering_strategy.order(filtered_examples).map do |example|
 next if RSpec.world.wants_to_quit
 instance = new(example.inspect_output)
 set_ivars(instance, before_context_ivars)
 succeeded = example.run(instance, reporter)
 RSpec.world.wants_to_quit = true if fail_fast? && !succeeded
 succeeded
 end.all?
 end
56. Running One Example • Check that it is not pending • Run before blocks • instance_exec the block in the context of the example group • Raise is the example skips or fails • Run after blocks
57. begin
 run_before_example
 @example_group_instance.instance_exec(self, &@example_block)
 if pending?
 Pending.mark_fixed! self
 raise Pending::PendingExampleFixedError,
 'Expected example to fail since it is pending, but it passed.',
 [location]
 end
 rescue Pending::SkipDeclaredInExample
 # no-op, required metadata has already been set by the `skip`
 # method.
 rescue Exception => e
 set_exception(e)
 ensure
 run_after_example
 finish(reporter)
 end
58. begin
 run_before_example
 @example_group_instance.instance_exec(self, &@example_block)
 if pending?
 Pending.mark_fixed! self
 raise Pending::PendingExampleFixedError,
 'Expected example to fail since it is pending, but it passed.',
 [location]
 end
 rescue Pending::SkipDeclaredInExample
 # no-op, required metadata has already been set by the `skip`
 # method.
 rescue Exception => e
 set_exception(e)
 ensure
 run_after_example
 finish(reporter)
 end
59. begin
 run_before_example
 @example_group_instance.instance_exec(self, &@example_block)
 if pending?
 Pending.mark_fixed! self
 raise Pending::PendingExampleFixedError,
 'Expected example to fail since it is pending, but it passed.',
 [location]
 end
 rescue Pending::SkipDeclaredInExample
 # no-op, required metadata has already been set by the `skip`
 # method.
 rescue Exception => e
 set_exception(e)
 ensure
 run_after_example
 finish(reporter)
 end
60. begin
 run_before_example
 @example_group_instance.instance_exec(self, &@example_block)
 if pending?
 Pending.mark_fixed! self
 raise Pending::PendingExampleFixedError,
 'Expected example to fail since it is pending, but it passed.',
 [location]
 end
 rescue Pending::SkipDeclaredInExample
 # no-op, required metadata has already been set by the `skip`
 # method.
 rescue Exception => e
 set_exception(e)
 ensure
 run_after_example
 finish(reporter)
 end
61. begin
 run_before_example
 @example_group_instance.instance_exec(self, &@example_block)
 if pending?
 Pending.mark_fixed! self
 raise Pending::PendingExampleFixedError,
 'Expected example to fail since it is pending, but it passed.',
 [location]
 end
 rescue Pending::SkipDeclaredInExample
 # no-op, required metadata has already been set by the `skip`
 # method.
 rescue Exception => e
 set_exception(e)
 ensure
 run_after_example
 finish(reporter)
 end
62. begin
 run_before_example
 @example_group_instance.instance_exec(self, &@example_block)
 if pending?
 Pending.mark_fixed! self
 raise Pending::PendingExampleFixedError,
 'Expected example to fail since it is pending, but it passed.',
 [location]
 end
 rescue Pending::SkipDeclaredInExample
 # no-op, required metadata has already been set by the `skip`
 # method.
 rescue Exception => e
 set_exception(e)
 ensure
 run_after_example
 finish(reporter)
 end
63. Expectations and Matchers
64. expect(name.sort_name).to eq("Rappin, Noel”) ExpectationTarget.new(name.sortName)

65. An Expectation target responds to “to” and “not_to”
66. Which take a matcher as an argument and evaluate the matcher
67. A matcher responds to “matches?”
68. eq is a built in method of RSpec::Matchers def eq(expected)
 BuiltIn::Eq.new(expected)
 end
69. <ExpectationTarget#"Rappin, Noel">.to(Eq#"Rappin, Noel")
70. <ExpectationTarget#"Rappin, Noel">.to(Eq#"Rappin, Noel”) PositiveExpectationHandler.handle_matcher(“Rappin, Noel”, <EQ> def match(expected, actual)
 actual == expected
 end
71. Let’s look at a fancier trick expect(Name.new("Noel Rappin")).to be_valid
72. BE_PREDICATE_REGEX = /^(be_(?:an?_)?)(.*)/
 HAS_REGEX = /^(?:have_)(.*)/
 
 def method_missing(method, *args, &block)
 case method.to_s
 when BE_PREDICATE_REGEX
 BuiltIn::BePredicate.new(method, *args, &block)
 when HAS_REGEX
 BuiltIn::Has.new(method, *args, &block)
 else
 super
 end
 end
73. class BePredicate < BaseMatcher
 include BeHelpers
 
 def initialize(*args, &block)
 @expected = parse_expected(args.shift)
 @args = args
 @block = block
 end
 
 def matches?(actual, &block)
 @actual = actual
 @block ||= block
 predicate_accessible? && predicate_matches?
 end
 
 def predicate_accessible?
 actual.respond_to?(predicate) || actual.respond_to?(present_tense_predicate)
 end
 
 def predicate_matches?
 method_name = actual.respond_to?(predicate) ? predicate : present_tense_predicate
 @predicate_matches = actual.__send__(method_name, *@args, &@block)
 end
 end
74. 
 
 def matches?(actual, &block)
 @actual = actual
 @block ||= block
 predicate_accessible? && predicate_matches?
 end
 
 def predicate_accessible?
 actual.respond_to?(predicate) || actual.respond_to?(present_tense_predicate)
 end
 
 def predicate_matches?
 method_name = actual.respond_to?(predicate) ? predicate : present_tense_predicate
 @predicate_matches = actual.__send__(method_name, *@args, &@block)
 end
75. 
 
 def matches?(actual, &block)
 @actual = actual
 @block ||= block
 predicate_accessible? && predicate_matches?
 end
 
 def predicate_accessible?
 actual.respond_to?(predicate) || actual.respond_to?(present_tense_predicate)
 end
 
 def predicate_matches?
 method_name = actual.respond_to?(predicate) ? predicate : present_tense_predicate
 @predicate_matches = actual.__send__(method_name, *@args, &@block)
 end
76. 
 
 def matches?(actual, &block)
 @actual = actual
 @block ||= block
 predicate_accessible? && predicate_matches?
 end
 
 def predicate_accessible?
 actual.respond_to?(predicate) || actual.respond_to?(present_tense_predicate)
 end
 
 def predicate_matches?
 method_name = actual.respond_to?(predicate) ? predicate : present_tense_predicate
 @predicate_matches = actual.__send__(method_name, *@args, &@block)
 end
77. 
 
 def matches?(actual, &block)
 @actual = actual
 @block ||= block
 predicate_accessible? && predicate_matches?
 end
 
 def predicate_accessible?
 actual.respond_to?(predicate) || actual.respond_to?(present_tense_predicate)
 end
 
 def predicate_matches?
 method_name = actual.respond_to?(predicate) ? predicate : present_tense_predicate
 @predicate_matches = actual.__send__(method_name, *@args, &@block)
 end
78. Emoji
79. define_example_group_method :example_group
 define_example_group_method :describe
 define_example_group_method :context
 define_example_group_method :xdescribe,
 :skip => "Temporarily skipped with xdescribe"
 define_example_group_method :xcontext,
 :skip => "Temporarily skipped with xcontext"
 define_example_group_method :fdescribe,
 :focus => true
 define_example_group_method :fcontext,
 :focus => true
80. 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 :skip, :skip => true
 define_example_method :pending, :pending => true
81. require 'rails_helper'
 
 module RSpec
 module Core
 class ExampleGroup
 define_example_group_method :!
 define_example_method :" end
 end
 
 module Matchers
 def #(value=::RSpec::Expectations::ExpectationTarget::UndefinedValue, &block)
 ::RSpec::Expectations::ExpectationTarget.for(value, block)
 end
 alias_matcher :❤, :eq
 end
 end
82. And then… RSpec.! Hotel do
 " "works" do
 #(1 + 1).to ❤(2)
 end
 end
83. Mocks
84. Simple Mock Example require 'rails_helper'
 
 RSpec.describe Name do
 it "assigns a rating category" do
 user = User.new()
 expect(user).to receive(:credit_rating).and_return(1000)
 expect(user.rating_category).to eq("approved")
 end
 end
85. What would this mock need to do? •Ensure the method is not called •Track how often it’s called •Verify that expectations are met
86. Ruby Method Lookup path • Singleton class • instance methods of class • Included modules • parent of class • parent’s included modules • and so on…
87. Singleton Class class << x def foo #something end end def x.bar #something end x.foo; x.bar
88. Key Concepts • Receive is a matcher • Space • Proxy • Method Double Original Object Singleton Class MethodDouble Proxy Space Receive Matcher
89. Receive creates a matcher def receive(method_name, &block)
 Matchers::Receive.new(method_name, block)
 end
90. Inside the Receive Matcher def setup_expectation(subject, &block)
 warn_if_any_instance("expect", subject)
 @describable = setup_mock_proxy_method_substitute( subject, :add_message_expectation, block)
 end
 alias matches? setup_expectation
 
 def setup_mock_proxy_method_substitute(subject, method, block)
 proxy = ::RSpec::Mocks.space.proxy_for(subject)
 setup_method_substitute(proxy, method, block)
 end
91. Inside the Receive Matcher def setup_expectation(subject, &block)
 warn_if_any_instance("expect", subject)
 @describable = setup_mock_proxy_method_substitute( subject, :add_message_expectation, block)
 end
 alias matches? setup_expectation
 
 def setup_mock_proxy_method_substitute(subject, method, block)
 proxy = ::RSpec::Mocks.space.proxy_for(subject)
 setup_method_substitute(proxy, method, block)
 end
92. Inside the Receive Matcher def setup_expectation(subject, &block)
 warn_if_any_instance("expect", subject)
 @describable = setup_mock_proxy_method_substitute( subject, :add_message_expectation, block)
 end
 alias matches? setup_expectation
 
 def setup_mock_proxy_method_substitute(subject, method, block)
 proxy = ::RSpec::Mocks.space.proxy_for(subject)
 setup_method_substitute(proxy, method, block)
 end
93. Inside the Receive Matcher def setup_expectation(subject, &block)
 warn_if_any_instance("expect", subject)
 @describable = setup_mock_proxy_method_substitute( subject, :add_message_expectation, block)
 end
 alias matches? setup_expectation
 
 def setup_mock_proxy_method_substitute(subject, method, block)
 proxy = ::RSpec::Mocks.space.proxy_for(subject)
 setup_method_substitute(proxy, method, block)
 end
94. Proxy •Substitutes the doubled method •Tracks calls
95. Proxy adds Expectations def add_message_expectation(method_name, opts={}, &block)
 location = opts.fetch(:expected_from) { CallerFilter.first_non_rspec_line }
 meth_double = method_double_for(method_name)
 
 if null_object? && !block
 meth_double.add_default_stub(@error_generator, @order_group, location, opts) do
 @object
 end
 end
 
 meth_double.add_expectation @error_generator, @order_group, location, opts, &block
 end
96. Proxy adds Expectations def add_message_expectation(method_name, opts={}, &block)
 location = opts.fetch(:expected_from) { CallerFilter.first_non_rspec_line }
 meth_double = method_double_for(method_name)
 
 if null_object? && !block
 meth_double.add_default_stub(@error_generator, @order_group, location, opts) do
 @object
 end
 end
 
 meth_double.add_expectation @error_generator, @order_group, location, opts, &block
 end
97. Proxy adds Expectations def add_message_expectation(method_name, opts={}, &block)
 location = opts.fetch(:expected_from) { CallerFilter.first_non_rspec_line }
 meth_double = method_double_for(method_name)
 
 if null_object? && !block
 meth_double.add_default_stub(@error_generator, @order_group, location, opts) do
 @object
 end
 end
 
 meth_double.add_expectation @error_generator, @order_group, location, opts, &block
 end
98. Method Double def define_proxy_method
 return if @method_is_proxied
 save_original_method!
 definition_target.class_exec( self, method_name, visibility) do |method_double, method_name, visibility|
 define_method(method_name) do |*args, &block|
 method_double.proxy_method_invoked(self, *args, &block)
 end
 __send__(visibility, method_name)
 end
 @method_is_proxied = true
 end
 
 def proxy_method_invoked(_obj, *args, &block)
 @proxy.message_received method_name, *args, &block
 end
99. Method Double def define_proxy_method
 return if @method_is_proxied
 save_original_method!
 definition_target.class_exec( self, method_name, visibility) do |method_double, method_name, visibility|
 define_method(method_name) do |*args, &block|
 method_double.proxy_method_invoked(self, *args, &block)
 end
 __send__(visibility, method_name)
 end
 @method_is_proxied = true
 end
 
 def proxy_method_invoked(_obj, *args, &block)
 @proxy.message_received method_name, *args, &block
 end
100. Method Double def define_proxy_method
 return if @method_is_proxied
 save_original_method!
 definition_target.class_exec( self, method_name, visibility) do |method_double, method_name, visibility|
 define_method(method_name) do |*args, &block|
 method_double.proxy_method_invoked(self, *args, &block)
 end
 __send__(visibility, method_name)
 end
 @method_is_proxied = true
 end
 
 def proxy_method_invoked(_obj, *args, &block)
 @proxy.message_received method_name, *args, &block
 end
101. Method Double def define_proxy_method
 return if @method_is_proxied
 save_original_method!
 definition_target.class_exec( self, method_name, visibility) do |method_double, method_name, visibility|
 define_method(method_name) do |*args, &block|
 method_double.proxy_method_invoked(self, *args, &block)
 end
 __send__(visibility, method_name)
 end
 @method_is_proxied = true
 end
 
 def proxy_method_invoked(_obj, *args, &block)
 @proxy.message_received method_name, *args, &block
 end
102. Method Double def define_proxy_method
 return if @method_is_proxied
 save_original_method!
 definition_target.class_exec( self, method_name, visibility) do |method_double, method_name, visibility|
 define_method(method_name) do |*args, &block|
 method_double.proxy_method_invoked(self, *args, &block)
 end
 __send__(visibility, method_name)
 end
 @method_is_proxied = true
 end
 
 def proxy_method_invoked(_obj, *args, &block)
 @proxy.message_received method_name, *args, &block
 end
103. Expectations are verified after an example is torn down
104. See also http://rspec.info/documentation/
105. Noel Rappin Table XI @noelrap http://www.pragprog.com/book/nrtest2 (test2rappin for 25% off) http://www.noelrappin.com/trdd http://www.noelrappin.com/mstwjs