Testing for Android developers

Getting started with testing in Android in 2023 is easier than ever before. We will be covering some fundamentals of thoughts around testing as well as getting into actual examples of how to test your code.

Transcript

1. Jetpack Compose 21st of March @SthlmAndroid GDG Android Stockholm http://bit.ly/409agZ4
2. #sthlmtech #sthlmandroid #gdg #gdgandroidsthlm @SthlmAndroid GDG Android Stockholm
3. Agenda • Welcome to B3 (safety guidelines and brief company overview) • Pragmatic testing in Android by Peter • Jetpack Compose Animations by Erik • Snacks and mingle
5. Testing For Android developers Peter Törnhult @Citerus in/petertornhult medium.com/@peter.tornhult
7. Unit testing in Android • JUnit 3, 4 or 5 (other?) • Assertion libraries: ◦ org.junit.* ◦ Google Truth ◦ Kluent ◦ Hamcrest ◦ Gurken ◦ Etc… • Given, when, then • @VisibleForTesting • What NOT to test • Mock, stub, spy (Mockito or MockK) • Android context ◦ Mock ◦ Move to integration tests ◦ Robolectric
8. Unit testing
9. https://junit.org/junit4/ org.junit & JUnit 4
10. assertEquals(2, 1 + 1) assertNotEquals(1, 2) assertTrue(true) assertFalse(false) assertNull(null) assertNotNull(1) assertSame(1, 1) assertNotSame(128, 128) ... assertX(expected = …, actual = …)
11. @Test(expected = ArrayIndexOutOfBoundsException:: class) fun `test one exception old style` () { emptyArray<Int>()[ 0] } @Test fun `test multiple exceptions new style` () { assertThrows(ArrayIndexOutOfBoundsException:: class.java) { emptyArray<Int>()[ 0] } }
12. class Example { fun one() = 1 } class ExampleTest { private val example = Example() @Test fun `one should return 1` () { assertEquals( 1, Example().one()) } }
13. class Example { fun isCat(animal: Animal): Boolean { return if (animal is Cat) true else false } @Test fun `isCat should return true for Cats` () { assertTrue( example.isCat(Cat( "Whiskers"))) assertFalse( example.isCat(Dog( "Dogzilla")))}
14. class Example { fun isOne(input: Int): Boolean = input == 1 } @Test fun `isOne should return true for input 1` () { assertTrue( example.isOne(1)) assertFalse( example.isOne(-1)) assertFalse( example.isOne(0)) assertFalse( example.isOne(2)) }
15. @Before data class Example(var state: Any? = null) private val example = Example() @Test fun `state 1`() { assertNull( example.state) example.state = 1 assertEquals( 1, example.state) } @Test fun `state 2`() { assertNull( example.state) // Works in Unit tests example.state = 2 assertEquals( 2, example.state) }
16. @Before data class Example(var state: Any? = null) companion object { private val example = Example() } @Test fun `state 1`() { assertNull( example.state) example.state = 1 assertEquals( 1, example.state) } @Test fun `state 2`() { assertNull( example.state) // Fails example.state = 2 assertEquals( 2, example.state) }
17. @Before data class Example(var state: Any? = null) companion object { private lateinit var example: Example } @Before fun setUp() { example = Example() assertNull( example.state) } @Test fun `state 1`() { example.state = 1 assertEquals( 1, example.state) } @Test fun `state 2`() { example.state = 2 assertEquals( 2, example.state) }
18. @Before data class Example(var state: Any? = null) private lateinit var example: Example @Before fun setUp() { example = Example() }
19. @Before data class Example(var state: Any? = null) private lateinit var example: Example @Before fun setUp() { example = Example() } @Test fun `state can be changed` () { assertNull( example.state) example.state = 1_000L assertEquals( 1_000L, example.state) }
20. @After @After fun tearDown() { // Tear down, free resources }
21. @BeforeClass, @AfterClass companion object { private lateinit var example: Example @BeforeClass @JvmStatic fun setUpClass() { example = Example() } }
22. Given When Then
23. data class Example(var state: Any? = null) @Test fun `state can be changed` () { // Given val example = Example() // When example.state = 1_000L // Then assertEquals( 1_000L, example.state) }
24. data class Example(var state: Any? = null) // Given private val example = Example() @Test fun `state can be changed` () { // When example.state = 1_000L // Then assertEquals( 1_000L, example.state) }
25. ⇧⌘T or Ctrl+Shift+T
26. ⌘D or Alt+I
27. @VisibleForTesting class Example { @VisibleForTesting internal var state: Any? = null
28. What NOT to test / do • Dead code • Generated code • External libraries • No if-statements in tests • No sleep/pause/delay in tests • Hardware dependencies* class ExampleUnitTest { @Test fun addition_isCorrect () { assertEquals( 4, 2 + 2) } }
29. Stub A stub is an object that provides (canned) hardcoded values to method calls. It always returns the same output regardless of the input… Mock A mock is similar to a stub, but the behaviour of the mocked interface can be changed dynamically based on scenarios… Fake A Fake is an object with a concrete implementation that works similarly to the actual implementation… Spy A spy lets us verify what functions were called, with what arguments, when, and how often… Test double, Dummy…
30. https://mockk.io/
31. Fake / Test double interface ExampleRepo { fun one(): Int } class Example: ExampleRepo { override fun one() = 1 } class ExampleTest { private lateinit var example: Example private lateinit var exampleRepo : ExampleRepo @Before fun setUp() { example = Example() exampleRepo = object: ExampleRepo { override fun one(): Int = 1 } } }
32. Spy class Example{ fun isOne(input: Int): Boolean = input == 1 fun isNotOne(input: Int): Boolean = !isOne(input) @Test fun `isNotOne calls isOne once` () { val example = spyk(Example())
33. Spy class Example{ fun isOne(input: Int): Boolean = input == 1 fun isNotOne(input: Int): Boolean = !isOne(input) @Test fun `isNotOne calls isOne once` () { val example = spyk(Example()) example.isNotOne(2) verify { example.isOne(any()) }
34. Spy @Test fun `isNotOne calls isOne once` () { val example = spyk(Example()) example.isNotOne(2) verify { example.isOne(any()) } verify(exactly = 1) { example.isOne(2) } verify(exactly = 0) { example.isOne(1) } class Example{ fun isOne(input: Int): Boolean = input == 1 fun isNotOne(input: Int): Boolean = !isOne(input)
35. Mock @Test fun `two returns 2 and calls one only once` () { val example = spyk(Example()) val metaExample = MetaExample(example) assertEquals( 2, metaExample.two()) verify(exactly = 1) { example.one() } } class MetaExample( private val exampleRepo : ExampleRepo , ) { fun two() = exampleRepo .one() * 2 }
36. Mock @Test fun `two returns 2 and calls one only once` () { val example: Example = mockk() val metaExample = MetaExample(example) assertEquals( 2, metaExample.two()) verify(exactly = 1) { example.one() } } class MetaExample( private val exampleRepo : ExampleRepo , ) { fun two() = exampleRepo .one() * 2 }
37. Mock @Test fun `two returns 2 and calls one only once` () { val example: Example = mockk { every { one() } returns 1 } val metaExample = MetaExample(example) assertEquals( 2, metaExample.two()) verify(exactly = 1) { example.one() } } class MetaExample( private val exampleRepo : ExampleRepo , ) { fun two() = exampleRepo .one() * 2 }
38. Mock @Test fun `two calls one only once` () { val example: Example = mockk { every { one() } returns 1 } val metaExample = MetaExample(example) verify(exactly = 1) { example.one() } } class MetaExample( private val exampleRepo : ExampleRepo , ) { fun two() = exampleRepo .one() * 2 }
39. Mock @Test fun `two calls one only once` () { val example: Example = mockk(relaxed = true) val metaExample = MetaExample(example) verify(exactly = 1) { example.one() } } class MetaExample( private val exampleRepo : ExampleRepo , ) { fun two() = exampleRepo .one() * 2 }
40. MockK can also mock… https://mockk.io/ • Coroutines • Top level / Static functions • Extension functions • Objects • Private functions • … And supports • Varargs • Chained calls • unmocking • …
41. Integration testing
42. Integration testing
43. Flaky tests Start small
44. Flaky tests Start small - Verify app can start
45. Flaky tests Start small - Verify app can start - Verify home page is shown
46. Flaky tests Start small - Verify app can start - Verify home page is shown - Verify navigating to next screen works
47. Flaky tests Start small Remove all I/O from tests
48. Flaky tests Start small Remove all I/O from tests - Database (Room) -> In memory / fake
49. Flaky tests Start small Remove all I/O from tests - Database (Room) -> In memory / fake - Networking (OkHttp + Retrofit) -> Mock server + canned responses
50. Flaky tests Start small Remove all I/O from tests - Database (Room) -> In memory / fake - Networking (OkHttp + Retrofit) -> Mock server + canned responses - Local storage -> Mock repos or clear before each test
51. Flaky tests Start small Remove all I/O from tests - Database (Room) -> In memory / fake - Networking (OkHttp + Retrofit) -> Mock server + canned responses - Local storage -> Mock repos or clear before each test - Local files -> Mock repos or clear before each tests
52. Flaky tests Start small Remove all I/O from tests - Database (Room) -> In memory / fake - Networking (OkHttp + Retrofit) -> Mock server + canned responses - Local storage -> Mock repos or clear before each test - Local files -> Mock repos or clear before each tests - Other -> Mock
53. Flaky tests Start small Remove all I/O from tests Setup repeatable (non-random) data
54. Hilt ❤ Integration Tests @Module @TestInstallIn ( components = [SingletonComponent:: class], replaces = [AppDatabaseModule:: class] ) object FakeAppDatabaseModule { @Singleton @Provides fun providesAppDatabase (@ApplicationContext context: Context): AppDatabase = Room.inMemoryDatabaseBuilder(context. applicationContext, AppDatabase:: class.java) .setTransactionExecutor(Executors.newSingleThreadExecutor()) .build()
55. Espresso Basic view assertions
56. Espresso Basic view assertions Espresso test recorder
57. Espresso Basic view assertions Espresso test recorder Barista (https://github.com/AdevintaSpain/Barista)
58. Tests during migration to Compose
59. Tests during migration to Compose Espresso and ComposeTestRule can work together
60. Tests during migration to Compose Espresso and ComposeTestRule can work together but… Maybe just comment everything out 🤯 …at first
61. Compose testing Semantics tree - Tag Modifier.testTag("tag") composeTestRule .onNodeWithTag("tag") *Only supports strings
62. Compose testing Semantics tree - Tag - Text Text("text") composeTestRule .onNodeWithText("text")
63. Compose testing Semantics tree - Tag - Text - Content description Icon(contentDescription = "Icon", …) composeTestRule .onNodeWithContentDescription("Icon") *Only supports strings
64. Compose testing Semantics tree - Tag - Text - Content description - Missing performLongClick(...) Experimental, easy to add
65. Compose testing Semantics tree - Tag - Text - Content description - Missing performLongClick(...) - Missing pressBack() Use Espresso.pressBack()
66. Compose testing Semantics tree - Tag - Text - Content description - Missing performLongClick(...) - Missing pressBack() - Easy to use and extend
67. Compose testing Semantics tree - Tag - Text - Content description - Missing performLongClick(...) - Missing pressBack() - Easy to use and extend See Kakao
68. How and where to run Integration tests Local emulator(s) Local test device(s) Google Test Lab (or similar) Managed devices
69. UI testing
70. Paparazzi - https://github.com/cashapp/paparazzi Applitools - https://applitools.com/ Spoon (very old)
71. E2E testing
72. Manual testing
73. Android developer Meetup organizer Blogger Speaker in/petertornhult medium.com/@peter.tornhult Thank you!