Unit Testing- What, Why and How?

Slides covering few aspects of Unit Testing:
🔹 Why testing is important
🔹 What are the various testing types?
🔹 Tools and Frameworks for Unit Testing
🔹 Get familiar with testing annotations
🔹 How to write tests?
🔹 How to write testable code?

Session Link : https://www.youtube.com/watch?v=JC2s8iCoQm8&t=4897s&ab_channel=Recro

Transcript

1. Unit Testing: What, Why and How?
   Niharika Arora
   Senior Software Engineer, 1mg
   

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2. Agenda
   ● Why Tests?
   

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3. Agenda
   ● Why Tests?
   ● Tools and Frameworks
   

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4. Agenda
   ● Why Tests?
   ● Tools and Frameworks
   ● Demo
   

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5. Agenda
   ● Why Tests?
   ● Tools and Frameworks
   ● Demo
   ● Writing Testable Code
   

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7. ● “Mobile apps are frontend apps, the real logic is in the backend, so
   backend apps should be tested instead.”
   

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8. ● “Mobile apps are frontend apps, the real logic is in the backend, so
   backend apps should be tested instead.”
   ● “Mobile apps are difficult to unit test, because most of the logic is done
   in the UI. At most, you should only care about UI tests.”
   

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9. ● “Mobile apps are frontend apps, the real logic is in the
   backend, so backend apps should be tested instead.”
   ● “Mobile apps are difficult to unit test, because most of the logic
   is done in the UI. At most, you should only care about UI tests.”
   ● “Mobile apps are “simple” or “tiny” compared to backend
   apps. Thus, effort should be put in the features instead of
   wasting time making tests.”
   

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10. Why test?
    

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12. Why test?
    ● No recurring cost of doing fixes when things break in
    production.
    

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13. Why test?
    ● No recurring cost of doing fixes when things break in
    production.
    ● Maintenance and Refactoring becomes easy.
    

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14. Why test?
    ● No recurring cost of doing fixes when things break in
    production.
    ● Maintenance and Refactoring becomes easy.
    ● Validating your changes.
    

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15. Why test?
    ● No recurring cost of doing fixes when things break in
    production.
    ● Maintenance and Refactoring becomes easy.
    ● Validating your changes.
    ● Debugging
    

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16. Why test?
    ● No recurring cost of doing fixes when things break in
    production.
    ● Maintenance and Refactoring becomes easy.
    ● Validating your changes.
    ● Debugging
    ● Simplify integration.
    

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17. Why test?
    ● No recurring cost of doing fixes when things break in
    production.
    ● Maintenance and Refactoring becomes easy.
    ● Validating your changes.
    ● Debugging
    ● Simplify integration.
    ● The list never ends.
    

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18. Testing Pyramid
    

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20. UI Tests
    

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21. UI Tests
    ● Interact with the UI of your app, they emulate the user behavior and
    assert UI results.
    

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22. UI Tests
    ● Interact with the UI of your app, they emulate the user behavior and
    assert UI results.
    ● Slowest and most expensive tests as they require a device/emulator to
    run.
    

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23. UI Tests
    ● Interact with the UI of your app, they emulate the user behavior and
    assert UI results.
    ● Slowest and most expensive tests as they require a device/emulator to
    run.
    ● Tools : Espresso and UI Automator
    

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24. Integration Tests
    

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25. Integration Tests
    ● When we need to check how our code interacts with other parts of the
    Android framework but without the complexity of the UI.
    

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26. Integration Tests
    ● How your code interacts with other parts of the Android framework
    but without the complexity of the UI.
    ● Don’t require a device/emulator to run
    

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27. Integration Tests
    ● How your code interacts with other parts of the Android framework
    but without the complexity of the UI.
    ● Don’t require a device/emulator to run
    ● Tools: Roboelectric.
    

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28. Unit Test
    

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29. Unit Test
    “ A software testing method by which
    individual units of code, are tested to
    determine whether they are fit for use.
    The smallest testable part of an application
    (Classes and Methods).
    

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30. Unit Test
    ● Fastest and least expensive tests as they don’t require a
    device/emulator to run.
    

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31. Unit Test
    ● Fastest and least expensive tests as they don’t require a
    device/emulator to run.
    ● Testing one logical unit/component guarantee that our component
    works properly for the set of inputs that we expect.
    

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32. Unit Test
    ● Fastest and least expensive tests as they don’t require a
    device/emulator to run.
    ● Testing one logical unit/component guarantee that our component
    works properly for the set of inputs that we expect.
    ● Tools : JUnit and Mockito
    

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33. Good rule of Thumb
    

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34. Anatomy of a unit test
    

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35. Anatomy of a unit test
    ▪ Arrange all necessary preconditions and inputs.
    

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36. Anatomy of a unit test
    ▪ Arrange all necessary preconditions and inputs.
    ▪ Act on the object or method under test.
    

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37. Anatomy of a unit test
    ▪ Arrange all necessary preconditions and inputs.
    ▪ Act on the object or method under test.
    ▪ Assert that the expected results have occurred.
    

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39. Android Unit Testing Tools &
    Frameworks
    

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40. Android Unit Testing Tools &
    Framework
    ● JUnit
    

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41. JUnit
    

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42. JUnit
    ● Testing a class/method that doesn't call Android APIs.
    

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43. JUnit
    ● Testing a class/method that doesn't call Android APIs.
    ● Assertion-based testing
    

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45. JUnit statement assertions
    assertFalse(condition)
    assertEquals(expected, actual, tolerance)
    assertNull(object)
    assertNotNull(object)
    assertSame(expected, actual)
    

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46. JUnit Annotations
    @Test
    @Before
    @After
    @BeforeClass
    @AfterClass
    @Ignore
    

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47. JUnit Limitations
    

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48. JUnit Limitations
    ● Your Object/class have external dependencies
    

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49. Android Unit Testing Tools &
    Framework
    ● JUnit
    ● Mockito
    

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50. Mockito
    “ A Java framework allowing the creation of test mock objects in
    automated unit tests .
    

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51. Mockito features
    ▪ Mocking
    

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52. @Mock
    private lateinit var loginModel: LoginModel
    

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53. Mockito features
    ▪ Mocking
    ▪ Stubbing
    

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54. `when`(UtilityClass.isNetworkConnected()).thenReturn(true)
    

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55. Mockito features
    ▪ Mocking
    ▪ Stubbing
    ▪ Argument matchers
    

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56. `when`(UtilityClass.isEmailValid(ArgumentMatchers.anyString())).thenReturn(true)
    

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57. Mockito features
    ▪ Mocking
    ▪ Stubbing
    ▪ Argument matchers
    ▪ Verifying number of invocations
    

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58. Mockito features
    ▪ Mocking
    ▪ Stubbing
    ▪ Argument matchers
    ▪ Verifying number of invocations
    ▪ Verifying order of invocations
    

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60. Mockito limitations
    

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61. Mockito limitations
    ▪ Cannot mock final classes
    

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62. Mockito limitations
    ▪ Cannot mock final classes
    ▪ Cannot mock static methods
    

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63. Mockito limitations
    ▪ Cannot mock final classes
    ▪ Cannot mock static methods
    ▪ Cannot mock final methods
    

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64. Mockito limitations
    ▪ Cannot mock final classes
    ▪ Cannot mock static methods
    ▪ Cannot mock final methods
    ▪ Cannot mock equals(), hashCode()
    

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65. Android Unit Testing Tools &
    Framework
    ● JUnit
    ● Mockito
    ● PowerMock
    

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66. PowerMock
    

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67. PowerMock
    ● Framework that extends other mock libraries such as
    Mockito with more powerful capabilities.
    

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68. PowerMock
    ● Framework that extends other mock libraries such as
    Mockito with more powerful capabilities.
    ● Enable mocking of static methods, constructors, final
    classes and methods, private methods, removal of static
    initializers and more.
    

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69. Writing Testable Code
    Or how not to lose your mind coding
    

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70. Writing Tests can be hard!
    

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71. When done right, results in a clean, easy to maintain codebase
    

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72. Good Unit Test
    

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73. Good Unit Test
    ● Easy to write
    

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74. Good Unit Test
    ● Easy to write
    ● Readable
    

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75. Good Unit Test
    ● Easy to write
    ● Readable
    ● Reliable
    

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76. Good Unit Test
    ● Easy to write
    ● Readable
    ● Reliable
    ● Fast
    

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77. Good Unit Test
    ● Easy to write
    ● Readable
    ● Reliable
    ● Fast
    ● Truly Unit
    

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79. Testable Code
    

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80. Deterministic
    

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81. Deterministic
    

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84. Can you guess why this code is non deterministic?
    

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85. Side Effects
    

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86. Red Flags
    ● Static properties and Fields
    

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87. Red Flags
    ● Singletons
    

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88. Red Flags
    ● Static Methods
    

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89. Rule of Thumb
    

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90. Rule of Thumb
    ● Write deterministic code
    ● Minimize side effects
    ● In essence, write pure functions
    Can impurity really be removed?
    ● As much as possible, extract it out and keep it contained
    

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91. “Writing a test is simple, but writing a code
    that can be tested is not so simple”
    

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92. References
    Github Link -
    https://github.com/niharika2810/UnitTesting-MVVM-Kotlin-Koin-Coroutines-Sa
    mple
    Medium link -
    https://thedroidlady.com/2019/07/10/unit-testing-in-mvvm-kotlin-databinding.ht
    ml
    

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93. Resources
    https://android.jlelse.eu/better-testing-with-mvvm-ae74d4d872bd
    https://blog.mindorks.com/mockito-cannot-mock-in-kotlin
    https://blog.mindorks.com/using-mockito-in-android-unit-testing-as-
    a-pro
    https://www.raywenderlich.com/195-android-unit-testing-with-mockit
    o
    https://medium.com/@mohitaunni/tdd-in-andoid-a-brief-story-part-1-
    22166d211750
    

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94. Let’s connect
    ● LinkedIn : https://www.linkedin.com/in/thedroidlady/
    ● Medium : https://medium.com/@nik.arora8059
    ● Github : https://github.com/niharika2810
    ● Twitter : https://twitter.com/theDroidLady
    ● Personal : https://thedroidlady.com/
    

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