When To Mock

What are mocks, what are the consequences of using them, and when should you use them?

Slides from my talk @PHPDorset on 2014/11/03.

1. @stuherbert When To Mock
2. @stuherbert Introductions When To Mock
3. @stuherbert of Unit Testing The Holy Grail When To Mock
4. @stuherbert When To Mock $ git clone git@github.com:foo/bar.git $ cd bar $ composer install $ phpunit
5. @stuherbert When To Mock $ git clone git@github.com:foo/bar.git $ cd bar $ composer install $ phpunit
6. @stuherbert When To Mock $ git clone git@github.com:foo/bar.git $ cd bar $ composer install $ phpunit
7. @stuherbert When To Mock $ git clone git@github.com:foo/bar.git $ cd bar $ composer install $ phpunit
8. @stuherbert Unit Tests Should Execute Straight Out Of The Box When To Mock
9. @stuherbert This Was Easy In The Pre-Web World When To Mock
10. @stuherbert • Our code wasn’t networked • Our code used embedded data storage engines • Our code wasn’t multi-user When To Mock
11. @stuherbert • Our code wasn’t networked • Our code used embedded data storage engines • Our code wasn’t multi-user When To Mock
12. @stuherbert • Our code wasn’t networked • Our code used embedded data storage engines • Our code wasn’t multi-user When To Mock
13. @stuherbert Self-Contained Our Code Was When To Mock
14. @stuherbert Pre-Web Architecture Diagram When To Mock
15. @stuherbert Pre-Web Architecture Diagram When To Mock
16. @stuherbert Pre-Web Architecture Diagram When To Mock Application Stack
17. @stuherbert Talks To Things Today’s Code When To Mock
18. @stuherbert Self Contained Today’s Code Is Anything But When To Mock
19. @stuherbert Our Code Has Evolved From This When To Mock Application Stack
20. @stuherbert Our Code Now Looks Like This When To Mock Database Cache 1 2 3 Internal Services External Services Controller Models Views Framework Libraries Libraries Libraries
21. @stuherbert Internally, More Complexity When To Mock Database Cache 1 2 3 Internal Services External Services Controller Models Views Framework Libraries
22. @stuherbert Internally, More Dependencies When To Mock Database Cache 1 2 3 Internal Services External Services Controller Models Views Framework Libraries Libraries Libraries
23. @stuherbert Storage Is Now A Service When To Mock Database Cache 1 2 3 Internal Services External Services Controller Models Views Framework Libraries Libraries Libraries
24. @stuherbert Functionality Is Now A Service When To Mock Database Cache 1 2 3 Internal Services External Services Controller Models Views Framework Libraries Libraries Libraries
25. @stuherbert Apps Are Now A Service To Users When To Mock Database Cache 1 2 3 Internal Services External Services Controller Models Views Framework Libraries Libraries Libraries
26. @stuherbert Unit Tests Should Execute Straight Out Of The Box When To Mock
27. @stuherbert Good Advice? Is This Still When To Mock
28. @stuherbert Still Good Advice? • Makes testing reproducible • Ease of use by new project members • Supports continuous integration When To Mock
29. @stuherbert Still Good Advice? • Makes testing reproducible • Ease of use by new project members • Supports continuous integration When To Mock
30. @stuherbert Still Good Advice? • Makes testing reproducible • Ease of use by new project members • Supports continuous integration When To Mock
31. @stuherbert Unit Tests Should Execute Straight Out Of The Box When To Mock ✓
32. @stuherbert Now Requires Help Making Unit Tests Execute Out Of The Box When To Mock
33. @stuherbert We Want To Unit Test Like This When To Mock Application Stack
34. @stuherbert Are Gone But Those Days When To Mock
35. @stuherbert Our App Now Needs These When To Mock Database Cache Internal Services External Services
36. @stuherbert If We Mock These When To Mock Database Cache Internal Services External Services
37. @stuherbert We Can Unit Test Without Them When To Mock Database Cache Internal Services External Services
38. @stuherbert & We Can Simulate Failure Too When To Mock Database Cache Internal Services External Services
39. @stuherbert Three Key Questions When To Mock
40. @stuherbert • Can we mock all the things? • Should we mock all the things? • Should we mock inside our app? When To Mock
41. @stuherbert • Can we mock all the things? • Should we mock all the things? • Should we mock inside our app? When To Mock
42. @stuherbert • Can we mock all the things? • Should we mock all the things? • Should we mock inside our app? When To Mock
43. @stuherbert All The Things? Can We Mock When To Mock
44. @stuherbert • Given enough time and effort, yes we can When To Mock
45. @stuherbert All The Things? Should We Mock When To Mock
46. @stuherbert • Who is going to build the mocks? • How do you prove your mock behaves accurately today? • How do you prove your mock still behaves accurately tomorrow? When To Mock
47. @stuherbert • Who is going to build the mocks? • How do you prove your mock behaves accurately today? • How do you prove your mock still behaves accurately tomorrow? When To Mock
48. @stuherbert • Who is going to build the mocks? • How do you prove your mock behaves accurately today? • How do you prove your mock still behaves accurately tomorrow? When To Mock
49. @stuherbert • A mock can only be as good as the author’s understanding of whatever is being mocked • Tests using rotted mocks will continue to pass, but the code will fail when shipped When To Mock
50. @stuherbert • A mock can only be as good as the author’s understanding of whatever is being mocked • Tests using rotted mocks will continue to pass, but the code will fail when shipped When To Mock
51. @stuherbert Test what we can, mock what we have to When To Mock
52. @stuherbert Inside Our App? Should We Mock When To Mock
53. @stuherbert Our Code? What Happens Inside When To Mock
54. @stuherbert • computation • branching • input / output When To Mock
55. @stuherbert • computation • branching • input / output When To Mock
56. @stuherbert • computation • branching • input / output When To Mock
57. @stuherbert Forming Execution Paths When To Mock
58. @stuherbert One Execution Path Each Unit Test Exercises When To Mock
59. @stuherbert Such As This When To Mock
60. @stuherbert Or This When To Mock
61. @stuherbert Or This When To Mock
62. @stuherbert The Code You Call? What Happens When You Mock When To Mock
63. @stuherbert Adding Mocks Shortens The Paths We Can Test When To Mock
64. @stuherbert Take A Code Path When To Mock
65. @stuherbert Inject A Mock When To Mock
66. @stuherbert Shorter Code Path When To Mock
67. @stuherbert Behind The Mock? But What About The Code When To Mock
68. @stuherbert ? Unreachable Code When To Mock ? ? ?
69. @stuherbert Unreachable Code Mocks Inside Your App Create When To Mock
70. @stuherbert Is Untestable Code Unreachable Code When To Mock
71. @stuherbert What Is The Risk From The Code That You Can’t Test? When To Mock
72. @stuherbert Key Questions • How do you prove your mock behaves accurately today? • How do you prove your mock still behaves accurately tomorrow? When To Mock
73. @stuherbert • How do you prove your mock behaves accurately today? • How do you prove your mock still behaves accurately tomorrow? When To Mock
74. @stuherbert • A mock can only be as good as the author’s understanding of whatever is being mocked • Tests using rotted mocks will continue to pass, but the code will fail when shipped When To Mock
75. @stuherbert The Best Approach Mocks Are Sometimes When To Mock
76. @stuherbert Why? When To Mock
77. @stuherbert Is Reachable Not Every Code Path When To Mock
78. @stuherbert Testing For Failure • How do you get bad responses from the code you call? • How do you trigger your error handling? When To Mock
79. @stuherbert To Test For Failure Mocks Are A Great Way When To Mock
80. @stuherbert In Summary When To Mock
81. @stuherbert Test what we can, mock what we have to When To Mock
82. @stuherbert Unit Tests Should Execute Straight Out Of The Box When To Mock
83. @stuherbert Unit Tests Should Execute Straight Out Of The Box When To Mock ✗
84. @stuherbert Unit Tests Should Execute Straight Out Of The Box As Long As Test Accuracy Is Not Compromised When To Mock ✓
85. @stuherbert Unit Tests Should Be One Of Several Layers In Your Test Strategy When To Mock
86. @stuherbert Use Other Layers To Test For Things You Can’t Prove Because Of Your Mocks When To Mock
87. @stuherbert • Storyplayer for factory acceptance testing • Behat / BDD for product acceptance testing When To Mock
88. @stuherbert Thank You Any Questions? When To Mock