1. Don’t Mock
Yourself Out
David Chelimsky
Articulated Man, Inc

3. http://martinfowler.com/articles/mocksArentStubs.html

4. Classical and
Mockist Testing

5. Classical and
Mockist Testing

6. Classical and
Mockist Testing

7. classicist mockist

8. merbist railsist

9. rspecist testunitist

11. ist bin ein
red herring

12. The big issue here
is when to use a
mock
http://martinfowler.com/articles/mocksArentStubs.html

13. agenda
๏ overview of stubs and mocks
๏ mocks/stubs applied to rails
๏ guidelines and pitfalls
๏ questions

14. test double

15. test stub
describe Statement do
it quot;uses the customer name in the headerquot; do
customer = stub(quot;customerquot;)
customer.stub(:name).and_return('Joe Customer')
statement = Statement.new(customer)
statement.header.should == quot;Statement for Joe Customerquot;
end
end

16. test stub
describe Statement do
it quot;uses the customer name in the headerquot; do
customer = stub(quot;customerquot;)
customer.stub(:name).and_return('Joe Customer')
statement = Statement.new(customer)
statement.header.should == quot;Statement for Joe Customerquot;
end
end

17. test stub
describe Statement do
it quot;uses the customer name in the headerquot; do
customer = stub(quot;customerquot;)
customer.stub(:name).and_return('Joe Customer')
statement = Statement.new(customer)
statement.header.should == quot;Statement for Joe Customerquot;
end
end

18. test stub
describe Statement do
it quot;uses the customer name in the headerquot; do
customer = stub(quot;customerquot;)
customer.stub(:name).and_return('Joe Customer')
statement = Statement.new(customer)
statement.header.should == quot;Statement for Joe Customerquot;
end
end

19. mock object
describe Statement do
it quot;logs a message when printedquot; do
customer = stub(quot;customerquot;)
customer.stub(:name).and_return('Joe Customer')
logger = mock(quot;loggerquot;)
statement = Statement.new(customer, logger)
logger.should_receive(:log).with(/Joe Customer/)
statement.print
end
end

20. mock object
describe Statement do
it quot;logs a message when printedquot; do
customer = stub(quot;customerquot;)
customer.stub(:name).and_return('Joe Customer')
logger = mock(quot;loggerquot;)
statement = Statement.new(customer, logger)
logger.should_receive(:log).with(/Joe Customer/)
statement.print
end
end

21. mock object
describe Statement do
it quot;logs a message when printedquot; do
customer = stub(quot;customerquot;)
customer.stub(:name).and_return('Joe Customer')
logger = mock(quot;loggerquot;)
statement = Statement.new(customer, logger)
logger.should_receive(:log).with(/Joe Customer/)
statement.print
end
end

22. mock object
describe Statement do
it quot;logs a message when printedquot; do
customer = stub(quot;customerquot;)
customer.stub(:name).and_return('Joe Customer')
logger = mock(quot;loggerquot;)
statement = Statement.new(customer, logger)
logger.should_receive(:log).with(/Joe Customer/)
statement.print
end
end

23. mock object
describe Statement do
it quot;logs a message when printedquot; do
customer = stub(quot;customerquot;)
customer.stub(:name).and_return('Joe Customer')
logger = mock(quot;loggerquot;)
statement = Statement.new(customer, logger)
logger.should_receive(:log).with(/Joe Customer/)
statement.print
end
end

24. method level
concepts

25. describe Statement do
it quot;logs a message when printedquot; do
customer = Object.new
logger = Object.new
customer.stub(:name).and_return('Joe Customer')
statement = Statement.new(customer, logger)
logger.should_receive(:log).with(/Joe Customer/)
statement.print
end
end

26. describe Statement do
it quot;logs a message when printedquot; do
customer = Object.new
logger = Object.new
customer.stub(:name).and_return('Joe Customer')
statement = Statement.new(customer, logger)
logger.should_receive(:log).with(/Joe Customer/)
statement.print
end
end

27. describe Statement do
it quot;logs a message when printedquot; do
customer = Object.new
logger = Object.new
customer.stub(:name).and_return('Joe Customer')
statement = Statement.new(customer, logger)
logger.should_receive(:log).with(/Joe Customer/)
statement.print
end
end

28. method stub
describe Statement do
it quot;logs a message when printedquot; do
customer = Object.new
logger = Object.new
customer.stub(:name).and_return('Joe Customer')
statement = Statement.new(customer, logger)
logger.should_receive(:log).with(/Joe Customer/)
statement.print
end
end

29. describe Statement do
it quot;logs a message when printedquot; do
customer = Object.new
logger = Object.new
customer.stub(:name).and_return('Joe Customer')
statement = Statement.new(customer, logger)
logger.should_receive(:log).with(/Joe Customer/)
statement.print
end
end

30. message expectation
describe Statement do
it quot;logs a message when printedquot; do
customer = Object.new
logger = Object.new
customer.stub(:name).and_return('Joe Customer')
statement = Statement.new(customer, logger)
logger.should_receive(:log).with(/Joe Customer/)
statement.print
end
end

31. things aren’t always
as they seem

32. describe Statement do
it quot;uses the customer name in the headerquot; do
customer = mock(quot;customerquot;)
statement = Statement.new(customer)
customer.should_receive(:name).and_return('Joe Customer')
statement.header.should == quot;Statement for Joe Customerquot;
end
end
class Statement
def header
quot;Statement for #{@customer.name}quot;
end
end

33. describe Statement do
it quot;uses the customer name in the headerquot; do
customer = mock(quot;customerquot;)
statement = Statement.new(customer)
customer.should_receive(:name).and_return('Joe Customer')
statement.header.should == quot;Statement for Joe Customerquot;
end
end
class Statement
def header
quot;Statement for #{@customer.name}quot;
end
end

34. describe Statement do
it quot;uses the customer name in the headerquot; do
customer = mock(quot;customerquot;)
statement = Statement.new(customer)
customer.should_receive(:name).and_return('Joe Customer')
statement.header.should == quot;Statement for Joe Customerquot;
end
end
class Statement
def header
quot;Statement for #{@customer.name}quot;
end
end

35. describe Statement do
it quot;uses the customer name in the headerquot; do
customer = mock(quot;customerquot;)
statement = Statement.new(customer)
customer.should_receive(:name).and_return('Joe Customer')
statement.header.should == quot;Statement for Joe Customerquot;
end
end
class Statement
def header
quot;Statement for #{@customer.name}quot;
end
end

36. describe Statement do
it quot;uses the customer name in the headerquot; do
customer = mock(quot;customerquot;)
statement = Statement.new(customer)
customer.should_receive(:name).and_return('Joe Customer')
statement.header.should == quot;Statement for Joe Customerquot;
end
end
message
expectation
class Statement
def header
quot;Statement for #{@customer.name}quot;
end
end

37. describe Statement do
it quot;uses the customer name in the headerquot; do
customer = mock(quot;customerquot;)
statement = Statement.new(customer)
customer.should_receive(:name).and_return('Joe Customer')
statement.header.should == quot;Statement for Joe Customerquot;
end
end
bound to
implementation
class Statement
def header
quot;Statement for #{@customer.name}quot;
end
end

38. describe Statement do
it quot;uses the customer name in the headerquot; do
customer = stub(quot;customerquot;)
customer.stub(:name).and_return('Joe Customer')
statement = Statement.new(customer)
statement.header.should == quot;Statement for Joe Customerquot;
end
end
class Statement
def header
quot;Statement for #{@customer.name}quot;
end
end

39. describe Statement do
it quot;uses the customer name in the headerquot; do
customer = stub(quot;customerquot;)
customer.stub(:name).and_return('Joe Customer')
statement = Statement.new(customer)
statement.header.should == quot;Statement for Joe Customerquot;
end
end
class Statement
def header
quot;Statement for #{@customer.name}quot;
end
end

40. describe Statement do
it quot;uses the customer name in the headerquot; do
customer = stub(quot;customerquot;)
customer.stub(:name).and_return('Joe Customer')
statement = Statement.new(customer)
statement.header.should == quot;Statement for Joe Customerquot;
end
end
class Statement
def header
quot;Statement for #{@customer.name}quot;
end
end

41. describe Statement do
it quot;uses the customer name in the headerquot; do
customer = stub(quot;customerquot;)
customer.stub(:name).and_return('Joe Customer')
statement = Statement.new(customer)
statement.header.should == quot;Statement for Joe Customerquot;
end
end
class Statement
def header
quot;Statement for #{@customer.name}quot;
end
end

42. describe Statement do
it quot;uses the customer name in the headerquot; do
customer = stub(quot;customerquot;)
customer.stub(:name).and_return('Joe Customer')
statement = Statement.new(customer)
statement.header.should == quot;Statement for Joe Customerquot;
end
end
????
class Statement
def header
quot;Statement for #{@customer.name}quot;
end
end

43. describe Statement do
it quot;uses the customer name in the headerquot; do
customer = stub(quot;customerquot;)
customer.stub(:name).and_return('Joe Customer')
statement = Statement.new(customer)
statement.header.should == quot;Statement for Joe Customerquot;
end
end
message
expectation
class Statement
def header
quot;Statement for #{@customer.name}quot;
end
end

44. describe Statement do
it quot;uses the customer name in the headerquot; do
customer = stub(quot;customerquot;)
customer.stub(:name).and_return('Joe Customer')
statement = Statement.new(customer)
statement.header.should == quot;Statement for Joe Customerquot;
end
end
bound to
implementation
class Statement
def header
quot;Statement for #{@customer.name}quot;
end
end

45. stubs are often
used like mocks

46. mocks are often
used like stubs

47. we verify stubs by
checking state after
an action

48. we tell mocks to
verify interactions

49. sometimes stubs
just make the
system run

50. when are
method stubs
helpful?

51. isolation from
non-determinism

52. random values

53. random values
class BoardTest < MiniTest::Unit::TestCase
def test_allows_move_to_last_square
board = Board.new(
:squares => 50,
:die => MiniTest::Mock.new.expect('roll', 2)
)
piece = Piece.new
board.place(piece, 48)
board.move(piece)
assert board.squares[48].contains?(piece)
end
end

54. time
describe Event do
it quot;is not happening before the start timequot; do
now = Time.now
start = now + 1
Time.stub(:now).and_return now
event = Event.new(:start => start)
event.should_not be_happening
end
end

55. isolation from
external dependencies

56. network access
Database
Interface Database
Subject
Network
Internets
Interface

57. network access
def test_successful_purchase_sends_shipping_message
ActiveMerchant::Billing::Base.mode = :test
gateway = ActiveMerchant::Billing::TrustCommerceGateway.new(
:login => 'TestMerchant', :password => 'password'
)
item = stub()
messenger = mock()
messenger.expects(:ship).with(item)
purchase = Purchase.new(gateway, item, credit_card, messenger)
purchase.finalize
end

58. network access
Stub
Database
Code Subject
Example
Stub
Network

59. network access
def test_successful_purchase_sends_shipping_message
gateway = stub()
gateway.stubs(:authorize).returns(
ActiveMerchant::Billing::Response.new(true, quot;ignorequot;)
)
item = stub()
messenger = mock()
messenger.expects(:ship).with(item)
purchase = Purchase.new(gateway, item, credit_card, messenger)
purchase.finalize
end

60. polymorphic
collaborators

61. strategies
describe Employee do
it quot;delegates pay() to payment strategyquot; do
payment_strategy = mock()
employee = Employee.new(payment_strategy)
payment_strategy.expects(:pay)
employee.pay
end
end

62. mixins/plugins
describe AgeIdentifiable do
describe quot;#can_vote?quot; do
it quot;raises if including does not respond to birthdatequot; do
object = Object.new
object.extend AgeIdentifiable
expect { object.can_vote? }.to raise_error(
/must supply a birthdate/
)
end
it quot;returns true if birthdate == 18 years agoquot; do
object = Object.new
stub(object).birthdate {18.years.ago.to_date}
object.extend AgeIdentifiable
object.can_vote?.should be(true)
end
end
end

63. when are
message expectations
helpful?

64. side effects
describe Statement do
it quot;logs a message when printedquot; do
customer = stub(quot;customerquot;)
customer.stub(:name).and_return('Joe Customer')
logger = mock(quot;loggerquot;)
statement = Statement.new(customer, logger)
logger.should_receive(:log).with(/Joe Customer/)
statement.print
end
end

65. caching
describe ZipCode do
it quot;should only validate oncequot; do
validator = mock()
zipcode = ZipCode.new(quot;02134quot;, validator)
validator.should_receive(:valid?).with(quot;02134quot;).once.
and_return(true)
zipcode.valid?
zipcode.valid?
end
end

66. interface discovery
describe quot;thing I'm working onquot; do
it quot;does something with some assistancequot; do
thing_i_need = mock()
thing_i_am_working_on = ThingIAmWorkingOn.new(thing_i_need)
thing_i_need.should_receive(:help_me).and_return('what I need')
thing_i_am_working_on.do_something_complicated
end
end

67. isolation testing

68. specifying/testing
individual
objects in isolation

69. good fit with lots of
little objects

71. all of these
concepts apply to
the non-rails
specific parts of
our rails apps

72. isolation testing the
rails-specific parts
of our applicationss

74. V
M
C

75. View
Controller
Model

76. Browser
Router
View
Controller
Model
Database

77. rails testing
๏ unit tests
๏ functional tests
๏ integration tests

78. rails unit tests
๏ model classes (repositories)
๏ model objects
๏ database

79. rails functional tests
๏ model classes (repositories)
๏ model objects
๏ database
๏ views
๏ controllers

80. rails functional tests
๏ model classes (repositories)
๏ model objects
๏ database
๏ views
๏ controllers

81. rails functional tests
๏ model classes (repositories)
๏ model objects
!DRY
๏ database
๏ views
๏ controllers

82. rails integration tests
๏ model classes (repositories)
๏ model objects
๏ database
๏ views
๏ controllers
๏ routing/sessions

83. rails integration tests
๏ model classes (repositories)
๏ model objects
๏ database
!DRY
๏ views
๏ controllers
๏ routing/sessions

84. the BDD approach

85. inherited from XP

86. customer specs
developer specs

88. rails integration tests
+ webrat
shoulda, context,
micronaut, etc

89. customer specs are
implemented as
end to end tests

90. developer specs
are implemented as
isolation tests

91. mocking and
stubbing
with rails

92. partials in view specs
describe quot;/registrations/new.html.erbquot; do
before(:each) do
template.stub(:render).with(:partial => anything)
end
it quot;renders the registration navigationquot; do
template.should_receive(:render).with(:partial => 'nav')
render
end
it quot;renders the registration form quot; do
template.should_receive(:render).with(:partial => 'form')
render
end
end

93. conditional branches in
controller specs
describe quot;POST createquot; do
describe quot;with valid attributesquot; do
it quot;redirects to list of registrationsquot; do
registration = stub_model(Registration)
Registration.stub(:new).and_return(registration)
registration.stub(:save!).and_return(true)
post 'create'
response.should redirect_to(registrations_path)
end
end
end

94. conditional branches in
controller specs
describe quot;POST createquot; do
describe quot;with invalid attributesquot; do
it quot;re-renders the new formquot; do
registration = stub_model(Registration)
Registration.stub(:new).and_return(registration)
registration.stub(:save!).and_raise(
ActiveRecord::RecordInvalid.new(registration))
post 'create'
response.should render_template('new')
end
end
end

95. conditional branches in
controller specs
describe quot;POST createquot; do
describe quot;with invalid attributesquot; do
it quot;assigns the registrationquot; do
registration = stub_model(Registration)
Registration.stub(:new).and_return(registration)
registration.stub(:save!).and_raise(
ActiveRecord::RecordInvalid.new(registration))
post 'create'
assigns[:registration].should equal(registration)
end
end
end

96. shave a few lines but
leave a little stubble
http://github.com/dchelimsky/stubble

97. stubble
describe quot;POST createquot; do
describe quot;with valid attributesquot; do
it quot;redirects to list of registrationsquot; do
stubbing(Registration) do
post 'create'
response.should redirect_to(registrations_path)
end
end
end
end

98. stubble
describe quot;POST createquot; do
describe quot;with invalid attributesquot; do
it quot;re-renders the new formquot; do
stubbing(Registration, :as => :invalid) do
post 'create'
response.should render_template('new')
end
end
it quot;assigns the registrationquot; do
stubbing(Registration, :as => :invalid) do
|registration|
post 'create'
assigns[:registration].should equal(registration)
end
end
end
end

99. chains
describe UsersController do
it quot;GET 'best_friend'quot; do
member = stub_model(User)
friends = stub()
friend = stub_model(User)
User.stub(:find).and_return(member)
member.stub(:friends).and_return(friends)
friends.stub(:favorite).and_return(friend)
get :best_friend, :id => '37'
assigns[:friend].should equal(friend)
end
end

100. chains
describe UsersController do
it quot;GET 'best_friend'quot; do
friend = stub_model(User)
User.stub_chain(:find, :friends, :favorite).
and_return(friend)
get :best_friend, :id => '37'
assigns[:friend].should equal(friend)
end
end

101. guidlines, pitfalls, and
common concerns

102. focus on roles
Mock Roles, not Objects
http://www.jmock.org/oopsla2004.pdf

103. keep things simple

104. avoid tight coupling

105. complex setup is a
red flag for design
issues

106. don’t stub/mock the
object you’re testing

107. impedes
refactoring

108. :refactoring => <<-DEFINITION
Improving design
without
changing behaviour
DEFINITION

109. what is behaviour?

111. false positives
describe RegistrationsController do
describe quot;GET 'pending'quot; do
it quot;finds the pending registrationsquot; do
pending_registration = stub_model(Registration)
Registration.should_receive(:pending).
and_return([pending_registration])
get 'pending'
assigns[:registrations].should == [pending_registration]
end
end
end
class RegistrationsController < ApplicationController
def pending
@registrations = Registration.pending
end
end

112. false positives
describe RegistrationsController do
describe quot;GET 'pending'quot; do
it quot;finds the pending registrationsquot; do
pending_registration = stub_model(Registration)
Registration.should_receive(:pending).
and_return([pending_registration])
get 'pending'
assigns[:registrations].should == [pending_registration]
end
end
end
class RegistrationsController < ApplicationController
def pending
@registrations = Registration.pending
end
end

113. false positives
describe Registration do
describe quot;#pendingquot; do
it quot;finds pending registrationsquot; do
Registration.create!
Registration.create!(:pending => true)
Registration.pending.should have(1).item
end
end
end
class Registration < ActiveRecord::Base
named_scope :pending, :conditions => {:pending => true}
end

114. false positives
describe Registration do
describe quot;#pendingquot; do
it quot;finds pending registrationsquot; do
Registration.create!
Registration.create!(:pending => true)
Registration.pending.should have(1).item
end
end
end
class Registration < ActiveRecord::Base
named_scope :pending, :conditions => {:pending => true}
end

115. false positives
describe Registration do
describe quot;#pendingquot; do
it quot;finds pending registrationsquot; do
Registration.create!
Registration.create!(:pending => true)
Registration.pending_confirmation.should have(1).item
end
end
end
class Registration < ActiveRecord::Base
named_scope :pending_confirmation, :conditions => {:pending => true}
end

116. false positives
describe Registration do
describe quot;#pendingquot; do
it quot;finds pending registrationsquot; do
Registration.create!
Registration.create!(:pending => true)
Registration.pending_confirmation.should have(1).item
end
end
end
class Registration < ActiveRecord::Base
named_scope :pending_confirmation, :conditions => {:pending => true}
end

117. cucumber

119. http://pragprog.com/titles/achbd/the-rspec-book
http://xunitpatterns.com/
growing object-oriented
Mock Roles, not Objects software, guided by tests
http://www.jmock.org/oopsla2004.pdf http://www.mockobjects.com/book/

120. http://blog.davidchelimsky.net/
http://www.articulatedman.com/
http://rspec.info/
http://cukes.info/
http://pragprog.com/titles/achbd/the-rspec-book

121. ruby frameworks

122. rspec-mocks
http://github.com/dchelimsky/rspec

123. mocha
http://github.com/floehopper/mocha

124. flexmock
http://github.com/jimweirich/flexmock

125. rr
http://github.com/btakita/rr

126. not a mock
http://github.com/notahat/not_a_mock