Your tests are mocking you

Test doubles (a.k.a. “mocks”) managed to gain a bad reputation over the years for causing unreadable and hard-to-maintain tests. Years of misuse led to some programmers advising against test doubles. Even though they are fundamental in the London school of Test Driven Development.

In this talk, Jakub will go back to the origins of the technique to explain scenarios when it's best used and look at common pitfalls. We’ll discuss various types of test doubles based on examples and show how to make them trustworthy. The key to success, as it turns out, will be a combination of contract (role) and collaboration tests.

Transcript

1. JAKUB ZALAS YOUR TESTS ARE MOCKING YOU PHP EDITION with
2. Jakub Zalas @jakub_zalas @jakzal mastodon.social/@jakub_zalas a.k.a. Kuba
3. * Quick introduction * Behaviour & Veri fi cation * The chain premise * Collaboration tests * Contract tests * Mocking hell PLAN
4. xUnit Test Patterns Refactoring Test Code Gerard Meszaros 2007
28. https://blog.thecodewhisperer.com/permalink/integrated-tests-are-a-scam Beware the Integrated Tests Scam J. B. Rainsberger / @jbrains
32. DATA CALCULATIONS ACTIONS Grokking Simplicity Eric Normand 2021
34. “TEST A CHAIN BY TESTING EACH LINK” MICHAEL "GEEPAW" HILL https://www.geepawhill.org/2018/01/16/underplayed-the-chain-premise-in-depth/
40. WE GET TO CHOOSE WHEN AND WHERE WE BREAK THE DEPENDENCY CHAIN FOR TESTING
41. COLLABORATION TESTS
42. xUnit Test Patterns Refactoring Test Code Gerard Meszaros 2007
43. INDIRECT INPUT
47. STUB
48. STUB
49. STUB A REAL OBJECT, BUT A DUMMY WOULD WORK AS WELL.
50. STUB
51. STUB HAND-CRAFTED A STUB
52. STUB
53. STUB HAND-CRAFTED A STUB A STUB VS A MOCKING FRAMEWORK
54. STUB
55. STUB HAND-CRAFTED A STUB
56. STUB HAND-CRAFTED A STUB A STUB VS A MOCKING FRAMEWORK
57. STUB
58. INDIRECT OUTPUT
62. SPY
63. SPY A SPY HAND-CRAFTED
64. MOCK OBJECT
65. MOCK OBJECT A MOCK OBJECT WITH A MOCKING FRAMEWORK
66. MOCK OBJECT A MOCK OBJECT HAND-CRAFTED
67. MOCK OBJECT A MOCK OBJECT HAND-CRAFTED
68. MOCK OBJECT WITH A MOCKING FRAMEWORK
69. MOCK OBJECT A MOCK OBJECT WITH A MOCKING FRAMEWORK
71. CONTRACT TESTS a.k.a. "Role tests"
78. UnusualSpendingSensorTest
79. UnusualSpendingSensorTest PaymentRepositoryContractTest PaymentRepositoryContractTest
87. SEALING THE CONTRACT
88. SEALING THE CONTRACT
89. SEALING THE CONTRACT
90. SEALING THE CONTRACT
91. SEALING THE CONTRACT
109. THANK YOU Verify behaviour, not implementation Mock roles, not objects Listen to your tests, let them guide your design Keep your tests as tidy as the codebase Leverage test doubles as a TDD tool @jakub_zalas @jakub_zalas @jakzal