The Anatomy of a Mocked Call

A talk about mocking, stubbing and the internal architecture of RSpec Mocks I gave at ruby nation 2014.

Transcript

1. The Anatomy of a mocked call
2. !/samphippen
3. Hello everyone :)
4. x
5. Really British
6. Really British (I make no apologies)
7. I’ve got some excellent tea if you want some
8. I can teach you how to make it properly
9. Why is testing?
10. x`
12. Tests force behaviour
13. Without tests Anything could happen
14. Unit Testing makes me happy :) !
15. Unit Testing makes me happy :) ! Sorry DHH :(
16. Stubbing and mocking
17. Stubbing
18. Fake response to a method
19. allow(x).to( receive(:foo).and_return(3) )
20. x.foo will return 3
21. Mocking
22. Testing methods get called
23. expect(x).to receive(:foo)
24. Test fails if x does not receive foo
25. expect(x).to receive(:foo).with(3)
26. expect(x).to( receive(:foo) .with(3) .exactly(4).times )
27. How does it work?
28. Stubs
29. it “does something” do allow(foo).to receive(:bar) expect(foo.bar).to eq(nil) end
30. it “does something” do allow(foo).to receive(:bar) expect(foo.bar).to eq(nil) end
31. allow is syntax sugar for AllowanceTarget.new
32. Allowance Target
33. Allowance Target TargetBase
34. AllowanceTarget calls #delegate_to with :setup_allowance on TargetBase
35. Allowance Target TargetBase
36. TargetBase defines #to on AllowanceTarget
37. Defined #to calls :setup_allowance on matchers passed to #to
38. Allowance Target TargetBase
39. it “does something” do allow(foo).to receive(:bar) expect(foo.bar).to eq(nil) end
40. Things passed to #to are called “matchers”
41. Receive is a commonly used mocking/stubbing matcher
42. AllowanceTarget#to calls setup_allowance on the passed matcher
43. Allowance Target TargetBase Allowance Target TargetBase Receive
44. Receive#setup_allowance creates a Mock Proxy for object
45. Receive#setup_allowance calls #add_stub on the Mock Proxy
46. Allowance Target TargetBase Receive Proxy
47. Proxy objects manage all mocks/stubs for an object
48. it “does something” do allow(foo).to receive(:bar) allow(foo).to receive(:baz) expect(foo.bar).to eq(nil) end
49. Proxy#add_stub creates a MethodDouble for the stubbed method
50. Allowance Target TargetBase Proxy Receive Method Double
51. MethodDouble saves the original implementation
52. MethodDouble creates stub implementation
53. it “does something” do allow(foo).to receive(:bar) expect(foo.bar).to eq(nil) end
54. it “does something” do allow(foo).to receive(:bar) expect(foo.bar).to eq(nil) end
55. foo.bar is the stubbed implementation
56. Call foo.bar
57. Method Double Call foo.bar
58. Method Double Call foo.bar Proxy
59. Method Double Call foo.bar Proxy Invokes stub
60. Method Double Call foo.bar Proxy Invokes stub Return value
61. it “does something” do allow(foo).to receive(:bar) expect(foo.bar).to eq(nil) end
62. RSpec manages lifecycle of mocks
63. RSpec::Mocks.setup
64. RSpec::Mocks.setup Your test
65. RSpec::Mocks.setup Your test RSpec::Mocks.verify
66. RSpec::Mocks.teardown RSpec::Mocks.setup Your test RSpec::Mocks.verify
67. All of this happens in a mock space
68. Allowance Target TargetBase Proxy Receive Method Double
69. RSpec::Mocks.teardown calls #reset_all on the current Space
70. Space#reset_all calls #reset on each proxy
71. Proxy#reset calls #reset on each MethodDouble
72. MethodDouble#reset returns original methods to objects
73. RSpec::Mocks.teardown RSpec::Mocks.setup Your test RSpec::Mocks.verify
74. Phew
75. Mocks
76. it “does something” do expect(foo).to receive(:bar).with(3) expect(foo.bar(3)).to eq(nil) end
77. expect is syntax sugar for ExpectationTarget.new
78. Expectation Target TargetBase Proxy Receive Method Double
79. Calls #setup_expectation
80. it “does something” do expect(foo).to receive(:bar).with(3) expect(foo.bar(3)).to eq(nil) end
81. Receive stores details of stubbed/ mocked implementation
82. Expectation Target TargetBase Proxy Receive Method Double
83. Method Double Call foo.bar Proxy Invokes stub Return value
84. Proxy callback checks arguments
85. Proxy raises if args don’t match
86. it “does something” do expect(foo).to receive(:bar).with(3) expect(foo.bar(3)).to eq(nil) end
87. RSpec::Mocks.teardown RSpec::Mocks.setup Your test RSpec::Mocks.verify
88. RSpec::Mocks.verify calls Space#verify_all
89. Space#verify_all calls #verify on each Proxy
90. Proxy raises if mock not called
91. And that’s how it all works :)
92. RSpec 3.0.0 is out Please use it
93. I came here to take back the colonies.
94. Let’s have some questions !/samphippen sam@funandplausible.com