Pragmatic Testing

(given at Droidcon Italy 2018 and Android Makers 2018)

You open a pull request only to find that some tests are now failing. What goes through your mind?

Did I break something? Do I need to update the tests? Just what is that test testing anyway?

Ideally, #2 would almost never be the case, as rewriting a test usually means it's lost the regression testing value of its original form. How can we get there though? There’s no one right way to write tests, and it’s surprisingly easy to fall into the trap of writing change tests. There are good patterns you can leverage to scale them and maximize their long term value. This talk will detail simple patterns you can follow for healthy, pragmatic testing with a focus on test design, correctness, and how these values can translate into better overall API design of your code.

Transcript

1. Pragmatic Testing Zac Sweers - Uber @pandanomic
2. Testing?
3. Testing!
4. @Test
5. @Test
6. Pragmatic Testing
7. Pragmatic? Testing
8. Goals ⚽
9. Non-Goals
10. Non-Goals • Convince you testing is worthwhile
11. Non-Goals • Convince you testing is worthwhile • UI Testing (Espresso, layouts, etc)
12. Non-Goals • Convince you testing is worthwhile • UI Testing (Espresso, layouts, etc) • Knock specific libraries
14. Boundaries
15. Calculator
16. Calculator add() subtract() multiply() divide() equal() clear()
17. Calculator InputManager DisplayManager CPU RAM add() subtract() multiply() divide() equal() clear()
18. InputManager DisplayManager CPU RAM add() subtract() multiply() divide() equal() clear()
19. InputManager DisplayManager CPU RAM add() subtract() multiply() divide() equal() clear()
20. InputManager DisplayManager CPU RAM add() subtract() multiply() divide() equal() clear()
21. InputManager DisplayManager CPU RAM add() subtract() multiply() divide() equal() clear()
22. InputManager DisplayManager CPU RAM
23. InputManager DisplayManager CPU RAM
24. @Test fun testAdd() { }a InputManager DisplayManager CPU RAM
25. @Test fun testAdd() { val calculator = Calculator() }a InputManager DisplayManager CPU RAM
26. @Test fun testAdd() { val cpu = mock(CPU::class.java) val calculator = Calculator() }a InputManager DisplayManager CPU RAM
27. @Test fun testAdd() { val cpu = mock(CPU::class.java) val ram = mock(RAM::class.java) val calculator = Calculator() }a InputManager DisplayManager CPU RAM
28. @Test fun testAdd() { val cpu = mock(CPU::class.java) val ram = mock(RAM::class.java) val display = mock(DisplayManager::class.java) val calculator = Calculator() }a InputManager DisplayManager CPU RAM
29. @Test fun testAdd() { val cpu = mock(CPU::class.java) val ram = mock(RAM::class.java) val display = mock(DisplayManager::class.java) val input = mock(InputManager::class.java) val calculator = Calculator() }a InputManager DisplayManager CPU RAM
30. @Test fun testAdd() { val cpu = mock(CPU::class.java) val ram = mock(RAM::class.java) val display = mock(DisplayManager::class.java) val input = mock(InputManager::class.java) val calculator = Calculator(cpu, ram, display, input) }a InputManager DisplayManager CPU RAM
31. @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) }a InputManager DisplayManager CPU RAM
32. @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) input.add(2, 2) }a InputManager DisplayManager CPU RAM
33. @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) input.add(2, 2) verify(cpu).setRam(ram) }a InputManager DisplayManager CPU RAM
34. @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) input.add(2, 2) verify(cpu).setRam(ram) verify(input).onInputReceived(2) }a InputManager DisplayManager CPU RAM
35. @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) input.add(2, 2) verify(cpu).setRam(ram) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) }a InputManager DisplayManager CPU RAM
36. @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) input.add(2, 2) verify(cpu).setRam(ram) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(input).onInputReceived("+") }a InputManager DisplayManager CPU RAM
37. @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) input.add(2, 2) verify(cpu).setRam(ram) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(input).onInputReceived("+") verify(ram).storeInRAM(2) }a InputManager DisplayManager CPU RAM
38. @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) input.add(2, 2) verify(cpu).setRam(ram) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(input).onInputReceived("+") verify(ram).storeInRAM(2) verify(cpu).loadInputToCpu("+") }a InputManager DisplayManager CPU RAM
39. @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) input.add(2, 2) verify(cpu).setRam(ram) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(input).onInputReceived("+") verify(ram).storeInRAM(2) verify(cpu).loadInputToCpu("+") verify(input).onInputReceived(2) }a InputManager DisplayManager CPU RAM
40. InputManager DisplayManager CPU RAM @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) input.add(2, 2) verify(cpu).setRam(ram) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(input).onInputReceived("+") verify(ram).storeInRAM(2) verify(cpu).loadInputToCpu("+") verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) }a
41. InputManager DisplayManager CPU RAM @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) input.add(2, 2) verify(cpu).setRam(ram) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(input).onInputReceived("+") verify(ram).storeInRAM(2) verify(cpu).loadInputToCpu("+") verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(ram).loadFromRam() }a
42. InputManager DisplayManager CPU RAM @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) input.add(2, 2) verify(cpu).setRam(ram) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(input).onInputReceived("+") verify(ram).storeInRAM(2) verify(cpu).loadInputToCpu("+") verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(ram).loadFromRam() verify(cpu).calculateSum(2, 2) }a
43. InputManager DisplayManager CPU RAM @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) input.add(2, 2) verify(cpu).setRam(ram) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(input).onInputReceived("+") verify(ram).storeInRAM(2) verify(cpu).loadInputToCpu("+") verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(ram).loadFromRam() verify(cpu).calculateSum(2, 2) verify(display).displayResult(4) }a
44. InputManager DisplayManager CPU RAM @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) input.add(2, 2) verify(cpu).setRam(ram) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(input).onInputReceived("+") verify(ram).storeInRAM(2) verify(cpu).loadInputToCpu("+") verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(ram).loadFromRam() verify(cpu).calculateSum(2, 2) verify(display).displayResult(4) }a
45. @Test fun testAdd() { input.add(2, 2) }a InputManager DisplayManager CPU RAM
46. @Test fun testAdd() { input.add(2, 2) }a registerInputListener(listener: Listener) InputManager DisplayManager CPU RAM
47. val captor = ArgumentCaptor.forClass(Listener::class.java) InputManager DisplayManager CPU RAM
48. val captor = ArgumentCaptor.forClass(Listener::class.java) verify(input).registerInputListener(captor.capture()) InputManager DisplayManager CPU RAM
49. val captor = ArgumentCaptor.forClass(Listener::class.java) verify(input).registerInputListener(captor.capture()) val listener = captor.value InputManager DisplayManager CPU RAM
50. @Test fun testAdd() { val captor = ArgumentCaptor.forClass(Listener::class.java) verify(input).registerInputListener(captor.capture()) val listener = captor.value input.add(2, 2) }a InputManager DisplayManager CPU RAM
51. @Test fun testAdd() { // Captor stuff input.add(2, 2) }a InputManager DisplayManager CPU RAM
52. InputManager DisplayManager CPU RAM @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) // Captor stuff... input.add(2, 2) verify(cpu).setRam(ram) listener.onNewInput(2) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) listener.onNewInput("+") verify(input).onInputReceived("+") verify(ram).storeInRAM(2) verify(cpu).loadInputToCpu("+") listener.onNewInput(2) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(ram).loadFromRam() verify(cpu).calculateSum(2, 2) verify(display).displayResult(4) }a
53. InputManager DisplayManager CPU RAM @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) // Captor stuff... input.add(2, 2) verify(cpu).setRam(ram) listener.onNewInput(2) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) listener.onNewInput("+") verify(input).onInputReceived("+") verify(ram).storeInRAM(2) verify(cpu).loadInputToCpu("+") listener.onNewInput(2) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(ram).loadFromRam() verify(cpu).calculateSum(2, 2) verify(display).displayResult(4) }a
54. InputManager DisplayManager CPU RAM @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) // Captor stuff... input.add(2, 2) verify(cpu).setRam(ram) listener.onNewInput(2) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) listener.onNewInput("+") verify(input).onInputReceived("+") verify(ram).storeInRAM(2) verify(cpu).loadInputToCpu("+") listener.onNewInput(2) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(ram).loadFromRam() verify(cpu).calculateSum(2, 2) verify(display).displayResult(4) }a
55. InputManager DisplayManager CPU RAM @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) // Captor stuff... input.add(2, 2) verify(cpu).setRam(ram) listener.onNewInput(2) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) listener.onNewInput("+") verify(input).onInputReceived("+") verify(ram).storeInRAM(2) verify(cpu).loadInputToCpu("+") listener.onNewInput(2) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(ram).loadFromRam() verify(cpu).calculateSum(2, 2) verify(display).displayResult(4) }a
56. InputManager DisplayManager CPU RAM @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) // Captor stuff... input.add(2, 2) verify(cpu).setRam(ram) listener.onNewInput(2) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) listener.onNewInput("+") verify(input).onInputReceived("+") verify(ram).storeInRAM(2) verify(cpu).loadInputToCpu("+") listener.onNewInput(2) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(ram).loadFromRam() verify(cpu).calculateSum(2, 2) verify(display).displayResult(4) }a
57. @Test fun testAdd() { verify(cpu).calculateSum(2, 2) verify(display).displayResult(4) }a InputManager DisplayManager CPU RAM
58. @Test fun testAdd() { verify(cpu).calculateSum(2, 2) // Actually 0 verify(display).displayResult(4) }a InputManager DisplayManager CPU RAM
59. @Test fun testAdd() { when(cpu.calculateSum(2, 2)).thenReturn(4) verify(cpu).calculateSum(2, 2) verify(display).displayResult(4) }a InputManager DisplayManager CPU RAM
60. InputManager DisplayManager CPU RAM @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) // Captor stuff... input.add(2, 2) verify(cpu).setRam(ram) listener.onNewInput(2) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) listener.onNewInput("+") verify(input).onInputReceived("+") verify(ram).storeInRAM(2) verify(cpu).loadInputToCpu("+") listener.onNewInput(2) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(ram).loadFromRam() when(cpu.calculateSum(2, 2)).thenReturn(4) verify(cpu).calculateSum(2, 2) verify(display).displayResult(4)
61. InputManager DisplayManager CPU RAM @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) // Captor stuff... input.add(2, 2) verify(cpu).setRam(ram) listener.onNewInput(2) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) listener.onNewInput("+") verify(input).onInputReceived("+") verify(ram).storeInRAM(2) verify(cpu).loadInputToCpu("+") listener.onNewInput(2) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(ram).loadFromRam() when(cpu.calculateSum(2, 2)).thenReturn(4) verify(cpu).calculateSum(2, 2) verify(display).displayResult(4)
62. InputManager DisplayManager CPU RAM @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) // Captor stuff... input.add(2, 2) verify(cpu).setRam(ram) listener.onNewInput(2) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) listener.onNewInput("+") verify(input).onInputReceived("+") verify(ram).storeInRAM(2) verify(cpu).loadInputToCpu("+") listener.onNewInput(2) verify(input).onInputReceived(2) verify(cpu).loadInputToCpu(2) verify(ram).loadFromRam() when(cpu.calculateSum(2, 2)).thenReturn(4) verify(cpu).calculateSum(2, 2) verify(display).displayResult(4)
63. @Test fun testAdd() { // Mocks... val calculator = Calculator(cpu, ram, display, input) // Captor stuff... input.add(2, 2) listener.onNewInput(2) listener.onNewInput("+") listener.onNewInput(2) when(cpu.calculateSum(2, 2)).thenReturn(4) verify(cpu).calculateSum(2, 2) verify(display).displayResult(4) }a InputManager DisplayManager CPU RAM
64. InputManager DisplayManager CPU RAM @Test fun testAdd() { val calculator = Calculator(cpu, ram, display, input) }a
65. InputManager DisplayManager CPU RAM @Test fun testAdd() { val calculator = Calculator(cpu, ram, display, input) assertThat(calculator.add(2, 2)).isEqualTo(4) }a
66. InputManager DisplayManager CPU RAM InputManager DisplayManager CPU RAM @Test fun testAdd() { val calculator = Calculator(cpu, ram, display, input) assertThat(calculator.add(2, 2)).isEqualTo(4) }a
67. DisplayManager CPU RAM InputManager DisplayManager CPU RAM @Test fun testAdd() { val calculator = Calculator(cpu, ram, display, input) assertThat(calculator.add(2, 2)).isEqualTo(4) }a
68. DisplayManager CPU RAM DisplayManager CPU RAM @Test fun testAdd() { val calculator = Calculator(cpu, ram, display) assertThat(calculator.add(2, 2)).isEqualTo(4) }a
69. DisplayManager RAM DisplayManager CPU RAM @Test fun testAdd() { val calculator = Calculator(cpu, ram, display) assertThat(calculator.add(2, 2)).isEqualTo(4) }a
70. DisplayManager CPU RAM @Test fun testAdd() { val calculator = Calculator(CPU(), ram, display) assertThat(calculator.add(2, 2)).isEqualTo(4) }a
71. @Test fun testAdd() { val calculator = Calculator(CPU(), ram, display) assertThat(calculator.add(2, 2)).isEqualTo(4) }a DisplayManager CPU RAM DisplayManager CPU RAM
72. DisplayManager CPU DisplayManager CPU RAM @Test fun testAdd() { val calculator = Calculator(CPU(), ram, display) assertThat(calculator.add(2, 2)).isEqualTo(4) }a
73. RAM
74. RAM interface RAMa{ <T>afunastoreInRAM(key:aString,avalue:aT) <T>afunaloadFromRam(key:aString):aT? }
75. class InMemoryRAM : RAMa{ private val store = mutableMapOf<String, Any>() override <T>afunastoreInRAM(key:aString,avalue:aT) { return store[key] = value } override <T>afunaloadFromRam(key:aString):aT? { return store[key] } }
76. InMemoryRAM
77. DisplayManager CPU InMemoryRAM @Test fun testAdd() { val ram = mock(RAM::class.java) val calculator = Calculator(CPU(), ram, display) assertThat(calculator.add(2, 2)).isEqualTo(4) }a
78. DisplayManager CPU InMemoryRAM @Test fun testAdd() { val ram = InMemoryRAM() val calculator = Calculator(CPU(), ram, display) assertThat(calculator.add(2, 2)).isEqualTo(4) }a
79. CPU DisplayManager CPU @Test fun testAdd() { val ram = InMemoryRAM() val calculator = Calculator(CPU(), ram, display) assertThat(calculator.add(2, 2)).isEqualTo(4) }a
80. CPU DisplayManager CPU @Test fun testAdd() { val cpu = CPU(InMemoryRAM()) val calculator = Calculator(cpu, display) assertThat(calculator.add(2, 2)).isEqualTo(4) }a
81. CPU CPU DisplayManager @Test fun testAdd() { val cpu = CPU(InMemoryRAM()) val calculator = Calculator(cpu, display) assertThat(calculator.add(2, 2)).isEqualTo(4) }a DisplayManager
82. CPU CPU DisplayManager verify(display).displayResult(4) DisplayManager
83. CPU CPU DisplayManager verify(display).displayResult(4) assertThat(display.getCurrentResult()).isEqualTo(4) DisplayManager
84. CPU CPU DisplayManager verify(display).displayResult(4) assertThat(display.getCurrentResult()).isEqualTo(4) assertThat(display.recordedResults[0]).isEqualTo(4) DisplayManager
85. CPU CPU val resultHandler = RecordingResultHandler() // Calc assertThat(resultHandler.results[0]).isEqualTo(4) ResultHandler
86. CPU ResultHandler CPU @Test fun testAdd() { val cpu = CPU(InMemoryRAM()) val resultHandler = RecordingResultHandler() val calculator = Calculator(cpu, resultHandler) calculator.add(2, 2) assertThat(resultHandler.results[0]).isEqualTo(4) }a
87. CPU @Test fun testAdd() { val cpu = CPU(InMemoryRAM()) val calculator = Calculator(cpu) assertThat(calculator.add(2, 2)).isEqualTo(4) }a
88. val cpu = CPU(InMemoryRAM()) val calculator = Calculator(cpu) @Test fun testAdd() { assertThat(calculator.add(2, 2)).isEqualTo(4) }a
89. val cpu = CPU(InMemoryRAM()) val calculator = Calculator(cpu) @Testa fun testAdd() { assertThat(calculator.add(2, 2)).isEqualTo(4) }a @Testb fun testSub() { assertThat(calculator.subtract(2, 2)).isEqualTo(0) }b @Testc fun testMultiply() { assertThat(calculator.multiply(2, 2)).isEqualTo(4) }c
90. val cpu = CPU(InMemoryRAM()) val calculator = Calculator(cpu) @Testa fun testAdd() { assertThat(calculator.add(2, 2)).isEqualTo(4) }a
91. val cpu = CPU(InMemoryRAM()) val resultHandler = RecordingResultHandler() val calculator = Calculator(cpu, resultHandler) @Test fun testAdd() { calculator.add(2, 2) calculator.add(2, 3) calculator.add(2, -1) assertThat(resultHandler.results) .containsExactly(4, 5, 1) }a
92. Failure
93. @Test fun foo() { try { foo.bar() } catch (e: Exception) { // Expected } }a
94. @Test(expected = Exception::class) fun foo() { foo.bar() }a
95. @Test(expected = ExpectedException::class) fun foo() { foo.bar() }a
96. @Test() fun foo() { try { foo.bar() } catch (e: ExpectedException) { assertThat(e) .hasMessageThat() .contains("Oh no") }b }a
97. @Test() fun foo() { try { foo.bar() throw AssertionError("No") } catch (e: ExpectedException) { assertThat(e) .hasMessageThat() .contains("Oh no") }b }a
98. RxJava
99. @Test() fun rx() { Observable.error() .subscribe() }a
100. @Test() fun rx() { Observable.error() .subscribe() }a
101. throw error
102. // throw error Thread currentThread = Thread.currentThread(); UncaughtExceptionHandler handler = currentThread.getUncaughtExceptionHandler(); handler.uncaughtException(currentThread, error);
103. // throw error Thread currentThread = Thread.currentThread(); UncaughtExceptionHandler handler = currentThread.getUncaughtExceptionHandler(); handler.uncaughtException(currentThread, error); https://github.com/uber/AutoDispose/blob/master/autodispose/src/test/java/com/uber/ autodispose/RxErrorsRule.java
104. TestObserver
105. TestObserver Observable.just(1) .test()
106. TestObserver Observable.just(1) .test() .assertValue(...)
107. TestObserver Observable.just(1) .test() .assertValue(...) .assertError(...)
108. TestObserver Observer<Integer> o = mock(Observer::class.java) Observable.just(1) .subscribe(o) verify(o).onNext(...) verify(o).onError(...)
109. TestObserver Observable.just(1) .test() .assertValue(...) .assertError(...) .awaitDone(...)
110. Some others quickly because ⏰
111. What about my architecture?
112. class Calculator(val cpu: CPU, val resultHandler: ResultHandler, val inputManager: InputManager)
113. class CalculatorPresenter(val cpu: CPU, val resultHandler: ResultHandler, val inputManager: InputManager)
114. class CalculatorPresenter(val cpu: CPU, val resultHandler: ResultHandler, val inputManager: InputManager) Courtesy of Nick Butcher (@crafty)
115. class CalculatorPresenter(val cpu: CPU, val resultHandler: ResultHandler, val inputManager: InputManager) 0.0 7 8 9 4 5 6 1 2 3 C 0 ⏎
116. class CurrentValueView : ResultHandler 0.0 7 8 9 4 5 6 1 2 3 C 0 ⏎
117. class NumberInputManager : InputManager class CurrentValueView : ResultHandler 0.0 7 8 9 4 5 6 1 2 3 C 0 ⏎
118. class NumberInputManager : InputManager class CurrentValueView : ResultHandler 0.0 7 8 9 4 5 6 1 2 3 C 0 ⏎ class ImeInputManager : InputManager
119. class NumberInputManager : InputManager class CurrentValueView : ResultHandler 7 8 9 4 5 6 1 2 3 C 0 ⏎ 0.0
120. What about DI?
121. class MainActivity : Activity { @Inject lateinit var foo: Foo @Inject lateinit var bar: Bar }
122. @Test fun testActivity() { val activity = ... activity.foo = TestFoo() activity.bar = MockBar() }
123. @Test fun testActivity() { val activity = MainActivityTestHelper.create( TestFoo(), MockBar() )a }b
124. @Test fun testActivity() { val activity = MainActivityTestHelper.create( TestFoo(), MockBar() )a }b RIBS: https://github.com/uber/RIBs/blob/master/android/libraries/rib- compiler-test/src/main/java/com/uber/rib/compiler/ InteractorTestGenerator.java Injection Helper: https://github.com/dinosaurwithakatana/injection- helper
125. What about state?
126. State machines!
127. In short
128. Value is the boundary
129. Value is the boundary assertThat(calculator.add(2, 2)).isEqualTo(4) assertThat(resultHandler.results[0]).isEqualTo(4) Observable.just(1) .test() .assertValue(...) .assertError(...) .awaitDone(...)
130. Fakes are worth writing
131. Fakes are worth writing class InMemoryRAM : RAM { private val store = mutableMapOf<String, Any>() override <T> fun storeInRAM(key: String, value: T) { return store[key] = value } override <T> fun loadFromRam(key: String): T? { return store[key] } }
132. Ship your fakes
133. Ship your fakes fun test(): TestObserver<T> TestScopeProvider Room.inMemoryDatabaseBuilder(...)
134. Tests should test the public API
135. Tests should test the public API Semver your tests!
136. Test are prod code
137. Failures should be designed for
138. Failures should be designed for throw AssertionError("Should have crashed before this") catch (e: ExpectedException) { assertThat(e).isWhatWeExpected() } @Rule val errorsRule = RxErrorsRule()
139. More than one right way
140. Keep it simple.
141. Keep it pragmatic.
142. Further reading • Boundaries: https:// www.destroyallsoftware.com/talks/boundaries • Square libraries • RxJava • AutoDispose
143. Fini, merci! Zac Sweers - Uber @pandanomic