Unit Testing: Control Your Dependencies!

How to turn dependencies around so you can write code that is testable. Includes an example of testing networking code.

Transcript

1. Unit Testing:
 Control Your Dependencies! Jon Reid — @qcoding
 Facebook
2. Write a failing test Make the test pass Refactor
3. UI? Networking?
4. UI! Networking!
5. http://www.flickr.com/photos/jsmoorman/2298671281 3 Types of
 Unit Tests: ! Return Value Test ! State Test ! Interaction Test
6. Return Value Test Arrange: Set up object Act: Call method that returns a value Assert: Compare against expected value Test SUT call method value System Under Test
7. State Test Arrange: Set up object Act: Call method Assert: Query object in some way Test SUT call method result query
8. Interaction Test Test SUT Something Else! ? ?
9. Interaction Test Table GetDishes Waiter Cook ProcessOrder
10. Interaction Test Table GetDishes Waiter Cook ProcessOrder Fake Cook
11. Dependency Injection Table GetDishes Waiter Cook ProcessOrder Fake Cook
12. Dependency Injection • Extract and Override • Method Injection • Property Injection • Constructor Injection http://www.flickr.com/photos/8499561@N02/2755481069
14. Seams http://www.flickr.com/photos/gileslane/2262575575
15. Extract and Override
16. Extract and Override
17. Method Injection
18. Method Injection
19. Property Injection
20. Property Injection
21. Property Injection
22. Constructor Injection
23. Dependency Injection • Extract and Override • Method Injection • Property Injection • Constructor Injection • Ambient Context http://www.flickr.com/photos/8499561@N02/2755481069
24. Dependency Injection M A N N I N G Mark Seemann FOREWORD BY GLENN BLOCK in .NET
25. Interaction Test SUT Real Thing SUT Fake Thing Production Testing ?
26. Types of Fakes M A N N I N G the art of with examples in C# FOREWORDS BY Michael Feathers Robert C. Martin SECOND EDITION ROY OSHEROVE
27. Stub Test SUT Stub communicate assert (Fake)
28. Mock Test SUT Mock communicate assert (Fake)
29. “That’s great, Jon. …But how do I use this for networking?”
30. Networking Call Inject dependency
31. Networking Call Record number of calls
32. Networking Call Fake return value
33. Networking Call Capture arguments
34. Let’s Make a Fake
35. Let’s Make a Fake: 1. Stub the method
36. Let’s Make a Fake: 2. Record number of calls
37. Let’s Make a Fake: 3. Fake return value
38. Let’s Make a Fake: 4. Capture arguments
39. Let’s Write a Test (1): Does it call GET exactly once? 1. Arrange ! 2. Act
 3. Assert
40. Let’s Write a Test (2): Simulate a JSON Response!
41. Refactor Test Code: Spot Duplication
42. Refactor Test Code: Move Variables into Test Fixture
43. Refactor Test Code: Use Test Fixture
44. Refactor Test Code: Extract Helper Method Refactor test code to express the scenario
45. Let’s Make a Fake • Stub the method • Record number of calls • Fake return value • Capture arguments Fake Cook
46. Dependency Injection • Extract and Override • Method Injection • Property Injection • Constructor Injection http://www.flickr.com/photos/8499561@N02/2755481069
47. http://www.flickr.com/photos/jsmoorman/2298671281 3 Types of
 Unit Tests: ! Return Value Test ! State Test ! Interaction Test
48. QualityCoding.org @qcoding • Working Effectively with Legacy Code by Michael Feathers • Dependency Injection in .NET by Mark Seemann • The Art of Unit Testing by Roy Osherove • Test-Driven iOS Development by Graham Lee Resources