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Intro to Mocking - DjangoCon 2015
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: WhyUnit Testing Doesn’t Have to Be So Hard! Daniel Davis @Ooblioob
- 2. • Software Developerfor 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…
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- 5. • Struggled withunit testing until I learned about Mocking Learning To Test 5
- 6. Me Learning aboutMocking… 6 Image credit: http://stylecaster.com/excited-gif/
- 7. Many of usare in the same boat… 7
- 8. • “I wishsomeone would just give a talk on this…” • So if that’s you… We all want to write better tests…
- 9. Let’s Talk About UnitTests…
- 10. Unit – 70% Integration –20% UI 10% Testing Types
- 11. • “They’re goodwhen 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 testingeasier! 12
- 13. What Are Mocks? 13 TestDouble Dummy Object Test Stub Test Spy Mock Object Fake Object Commonly referred to as “Mocks”
- 14. • Stubs – Providea 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 Blahprofessor Dan… 15
- 16. • Eliminates dependencies –Isolated Unit Tests Problems Mocks Solve 16 foo(x) bar(x)
- 17. • Tests methodsthat have no return value Problems Mocks Solve 17 How do we know that bar(x) has been called?
- 18. • Tests errorhandling Problems Mocks Solve 18
- 19. • Eliminate dependencyon 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… Showme 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
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- 23. Problem: Tinder Competitor True loveis 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 amethod 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 noone could have seen EVERYONE in the database!!!” - The Intern get_next_person() get_random_person()
- 26. Write a UnitTest… 26
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- 30. Easy enough… 30 What ifknew the result of get_random_person()???
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- 33. It works EVERYSINGLE TIME!!! 33
- 34. Variations on atheme 34
- 35. Variations on atheme 35
- 36. Variations on atheme 36
- 37. Variations on atheme 37 OMG, ContextManagers! WHAT???
- 38. But what ifwe call it multiple times??? 38
- 39. • What ifI want to test the while loop? Different results on multiple calls
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- 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 VerifyBehavior 43
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- 45. • When auser 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 wetest this??? No return values!!!
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- 50. Shouldn’t we checkthe other methods too? 50 We’d need to have multiple mocks to do that!!!
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- 55. Whew!!! Almost Done! The dayis 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/
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- 57. Sample Problem: Docker Paymentswith Stripe
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- 60. • Requires usto 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 triedMocking??? 61
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- 64. • Mocking makeswriting unit tests simpler – Eliminates dependencies – Verifies behavior – Tests error handling • You just need some practice! Remember This!
- 65. • http://mock.readthedocs.org/en/latest/ • PipInstall Mock (Python 2) • Create a simple class, then write tests! Try It On Your Own 65
- 66. Let’s Go Write SomeTests!!! 66
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