Intro to Mocking - DjangoCon 2015
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The document discusses the importance of mocking in unit testing, explaining how it simplifies the process by eliminating dependencies and verifying behavior. It provides various types of mocks and examples of their application, particularly in Python, to enhance the efficiency of tests. Key takeaways emphasize the need for practice in utilizing mocking to improve unit testing skills.
Intro to Mocking - DjangoCon 2015
- 1. Intro To Mocking: Why Unit Testing Doesn’t Have to Be So Hard! Daniel Davis @Ooblioob
- 2. • Software Developer for 8 years • Senior Consultant: Excella Consulting in Washington, DC • Fun Fact: – I ran the “Jingle All The Way” 5k dressed as a Giant Gingerbread man A Little About Me…
- 3. 3
- 5. • Struggled with unit testing until I learned about Mocking Learning To Test 5
- 6. Me Learning about Mocking… 6 Image credit: http://stylecaster.com/excited-gif/
- 7. Many of us are in the same boat… 7
- 8. • “I wish someone would just give a talk on this…” • So if that’s you… We all want to write better tests…
- 9. Let’s Talk About Unit Tests…
- 10. Unit – 70% Integration – 20% UI 10% Testing Types
- 11. • “They’re good when the problem is easy” – A rabbit hole of testing • “I spend too much time writing lots of code to test, so I give up” • “There’s just some stuff you can’t unit test” Great Unit Testing Myths
- 12. Mocking makes unit testing easier! 12
- 13. What Are Mocks? 13 Test Double Dummy Object Test Stub Test Spy Mock Object Fake Object Commonly referred to as “Mocks”
- 14. • Stubs – Provide a canned response to method calls • Spy – Real objects that behave like normal except when a specific condition is met • Mocks – Verifies behavior (calls) to a method What Are Mocks? 14
- 15. Blah Blah Blah professor Dan… 15
- 16. • Eliminates dependencies – Isolated Unit Tests Problems Mocks Solve 16 foo(x) bar(x)
- 17. • Tests methods that have no return value Problems Mocks Solve 17 How do we know that bar(x) has been called?
- 18. • Tests error handling Problems Mocks Solve 18
- 19. • Eliminate dependency on database calls – Speed up testing! • Reduce test complexity – Don’t have to write complex logic to handle behavior of methods not under test • Don’t have to wait to implement other methods Other Reasons Mocks Are Important 19
- 20. Ok, I’m sold… Show me how to actually do this… 20
- 21. • Mock (MagicMock) – Most robust, popular – Built-in as of Python 3.3! • flexmock – Based on Ruby’s flexmock • mox – Similar to Java’s EasyMock • Mocker • dingus – “record then assert” mocking library • fudge – Similar to Mockito • MiniMock – Simple mocking with DocTest What Are The Python Options? 21
- 23. Problem: Tinder Competitor True love is an isolated container… Image Credits: - http://www.forbes.com/sites/jjcolao/2013/04/08/tinder-for-business-dating-app-looks-to-conquer-other-matchmaking-verticals/ - https://blog.docker.com
- 24. • Create a method to return a new, random victim candidate – Must not show the same person – Must not show someone the user has already “swiped” on Problem: “Docker” dating app
- 25. Easy enough… 25 “Surely no one could have seen EVERYONE in the database!!!” - The Intern get_next_person() get_random_person()
- 26. Write a Unit Test… 26
- 27. It works!!! 27
- 28. Noooooooooo!!!!
- 29. 29
- 30. Easy enough… 30 What if knew the result of get_random_person()???
- 31. 31
- 33. It works EVERY SINGLE TIME!!! 33
- 34. Variations on a theme 34
- 35. Variations on a theme 35
- 36. Variations on a theme 36
- 37. Variations on a theme 37 OMG, ContextManagers! WHAT???
- 38. But what if we call it multiple times??? 38
- 39. • What if I want to test the while loop? Different results on multiple calls
- 40. Uh…umm… 40 UMM…
- 42. • Use patching / mocks to bring certainty to method calls • Eliminates dependencies on other code – Even unfinished code!!! • Lots of ways to do it, pick your favorite Recap: What did we learn? 42
- 43. Mocking to Verify Behavior 43
- 45. • When a user swipes right… • If the other user “likes” them: – Send them both a message with contact info • If the other user “dislikes” them: – Let the user down gently… • If the other user hasn’t evaluated yet: – Display the “give it time” message Problem: “Docker” matches
- 46. Implementation 46 How do we test this??? No return values!!!
- 50. Shouldn’t we check the other methods too? 50 We’d need to have multiple mocks to do that!!!
- 55. Whew!!! Almost Done! The day is almost over! You can sleep later! Image Credits: - http://www.clickhole.com/article/8-kittens-god-forbid-could-be-used-prop-wobbly-tab-1364 - http://stuffpoint.com/dogs/image/208632/adorable-corgi-puppies-running-ddddd-picture/
- 57. Sample Problem: Docker Payments with Stripe
- 60. • Requires us to call the API • Unclear what those numbers mean • Must create the stripe_token – Not a dictionary of CC fields – Encrypted That’s ridiculous… 60 There’s got to be a better way…
- 61. …have you tried Mocking??? 61
- 64. • Mocking makes writing unit tests simpler – Eliminates dependencies – Verifies behavior – Tests error handling • You just need some practice! Remember This!
- 65. • http://mock.readthedocs.org/en/latest/ • Pip Install Mock (Python 2) • Create a simple class, then write tests! Try It On Your Own 65
- 66. Let’s Go Write Some Tests!!! 66