Testing gone-right
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The document discusses best practices for testing with mocks in Ruby on Rails applications. It recommends that tests run fast by avoiding loading Rails and using factories, and that mocks should assert messages rather than state. Tests become more maintainable by mocking roles instead of concrete objects, and by isolating code into single responsibility classes rather than putting logic in fat models. When code is well-encapsulated with messages, mocks can make tests clearer; but mocks may indicate problems when they are difficult to set up or when tests become brittle.
Testing gone-right
- 1. Testing Gone Right from RubyConf 2011 and others @jwo - Jesse Wolgamott
- 2. What We’ll Talk Abouts
- 3. What We’ll Talk Abouts • Mock is not a 4 letter word • Fast tests. Really Fast. • Rails Models
- 4. Mock is not a 4 letter word
- 5. Mocks
- 6. Mocks • Mocks are not stubs
- 7. Mocks • Mocks are not stubs • Mocks assert Messages
- 8. Mocks • Mocks are not stubs • Mocks assert Messages • Assert on state => Stubbing
- 9. Mocks • Mocks are not stubs • Mocks assert Messages • Assert on state => Stubbing • Assert on messages => Mocking
- 10. Ruby + OOP + Mock
- 11. Ruby + OOP + Mock • is goood
- 12. Ruby + OOP + Mock • is goood • Objects should tell objects to do things
- 13. Ruby + OOP + Mock • is goood • Objects should tell objects to do things • (Tell don’t ask)
- 14. Ruby + OOP + Mock • is goood • Objects should tell objects to do things • (Tell don’t ask) • You tell to do things using messages
- 15. Mock Roles • Instead of mocking objects, try to mock roles • Wanting to mock concrete objects is a design smell
- 16. Example
- 17. Example • Restaurant system reserves tables • Instead of your interface talking to a ReservationService: • Talk to ReservationInterfaceHandler
- 18. Message Example class ReservationInterface def initialize(handler) @handler = handler end def select_table(table) @table = table end def submit_request @handler.reserve(@table) end end
- 19. And to Spec it describe ReservationInterface do let(:table){something_interesting_here} it "should tell the handler to reserve a table" do handler = double('reservation_handler') handler.should_receive(:reserve).with(table) machine = ReservationInterface.new(handler) machine.select_table(table) machine.submit_request end
- 20. Watch Out!
- 21. On APIs • Only Mock Types you own • Don’t mock boundary objects • If you do, you’ll duplicate code -> CODE SMELL
- 23. Other Mock Smells • Having to setup more than 3 lines -- that’s a code smell
- 24. Other Mock Smells • Having to setup more than 3 lines -- that’s a code smell • Mocking concrete objects -- that’s a code smell
- 25. Other Mock Smells • Having to setup more than 3 lines -- that’s a code smell • Mocking concrete objects -- that’s a code smell • When tests go brittle and developers declare mocks suck -- that’s a code smell
- 26. However
- 27. However • If you have a “standard” Rails app, programmed procedurally:
- 28. However • If you have a “standard” Rails app, programmed procedurally: • Mocks are not for you
- 29. However • If you have a “standard” Rails app, programmed procedurally: • Mocks are not for you • If you encapulate your code. If you hide information (OOP). If you use messages:
- 30. However • If you have a “standard” Rails app, programmed procedurally: • Mocks are not for you • If you encapulate your code. If you hide information (OOP). If you use messages: • Mocks are for you!
- 31. Mocks Don’t Suck
- 32. Mocks Don’t Suck • If your code is hard to test, you need better code
- 33. Mocks Don’t Suck • If your code is hard to test, you need better code • If you have a test that is HARD to setup, your class (or test) is doing too much
- 34. Mocks Don’t Suck • If your code is hard to test, you need better code • If you have a test that is HARD to setup, your class (or test) is doing too much • If you see tests with uber-mocks, the answer is not to delete mocks. It’s to isolate your tests
- 35. Fast Rails Tests
- 36. Out of the Box
- 37. Out of the Box • Most Rails apps start as CRUD apps
- 38. Out of the Box • Most Rails apps start as CRUD apps • Tests start fast-ish
- 39. Out of the Box • Most Rails apps start as CRUD apps • Tests start fast-ish • Like a frog, we don’t notice the increase
- 40. “fast” tests • Tests should run in under a second • The entire rspec test suite
- 41. How? • Don’t load rails
- 42. Example Spec Run Real Time Time With Rails .07 s 8.1 s Without 0.0007 s .8 s Rails
- 43. Avoid Factories
- 44. Avoid Factories • Instead, extract your code to classes with one single responsibility
- 45. Avoid Factories • Instead, extract your code to classes with one single responsibility • Rather than knowing everything about your object
- 46. Avoid Factories • Instead, extract your code to classes with one single responsibility • Rather than knowing everything about your object • Or, load methods via modules
- 47. Rails Models
- 48. Rails Models • Are Fat.
- 49. Rails Models • Are Fat. • Wait, isn’t that good?
- 50. Rails Models • Are Fat. • Wait, isn’t that good? • It’s better than controller logic
- 51. Rails Models • Are Fat. • Wait, isn’t that good? • It’s better than controller logic • But no.
- 52. What then?
- 53. What then? • Your models can have validations
- 54. What then? • Your models can have validations • Call out to policy or decision classes for business logic
- 55. What then? • Your models can have validations • Call out to policy or decision classes for business logic • Use Ruby Classes
- 56. What then? • Your models can have validations • Call out to policy or decision classes for business logic • Use Ruby Classes • Use Presenters
- 57. Example • Example of building a burrito that is delicious, and can know it’s delicious • In Isolation: https://gist.github.com/1281093 • Using Modules: https://gist.github.com/ 1281064
- 58. Credits Why you don’t get mock objects @gregmoeck Your tests are lying to you @chrismdp Fast Rails talk at gogoruco 2011 @coreyhaines Testing in Isolation. @garybernhardt destroyalldoftware.com
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