Transforming your Tests with Kotlin

We know we should write tests, and we know that Kotlin gives us some nice features to use in our code, so how can we put these two together? There are some really great ways that Kotlin is being used in test writing, and we'll look at a number of them. This will include features such as higher order functions and escaping back-ticks and how they can make your tests more expressive. We'll also look at some testing libraries that take advantage of Kotlin's features. At the end of this talk you'll walk away with an understanding of how you can use Kotlin to make your tests more enjoyable.

Transcript

1. Transforming Your Tests With Kotlin Victoria Gonda victoriagonda.com @TTGonda
2. Testing with Kotlin
3. https://twitter.com/TTGonda/status/1123025116139544576
4. Victoria Gonda • Android Engineer at Buffer • Author and Editor at RayWenderlich.com • Hedgehog and cat owner • she/her
5. Kotlin features
6. `Backticks`
7. https://twitter.com/skentphd/status/1123035724788453377 https://twitter.com/jshvarts/status/1123362376840040448
8. Without `Backticks` @Test fun whenDeleteIsCalled_onlyCorrespondingDataIsDeleted() { }
9. `Backticks` @Test fun `deleteUpdates only deletes corresponding data`() { }
10. `Backticks` java.lang.AssertionError: Assertion failed at package.Test.deleteUpdates only deletes corresponding data
11. Higher order functions
12. https://twitter.com/wakingrufus/status/ 1123053243800653825 https://twitter.com/RBusarow/status/ 1123057633261441024 https://twitter.com/jessewilson/status/ 1123055645824028672
13. Higher order functions fun verifyLinkOpen(expectedUrl: String, openLink: () -> Unit) { Intents.init() try { openLink() intended(allOf(hasAction(ACTION_VIEW), hasData(expectedUrl))) } finally { Intents.release() } }
14. Higher order functions verifyLinkOpen("https://buffer.com") { clickBufferButton() }
15. Screen Robots
16. Screen Robots class CalculatorScreenRobot : ScreenRobot<CalculatorScreenRobot>() { fun verifyTipIsCorrect(tip: String): CalculatorScreenRobot { return checkViewHasText(R.id.textTip, tip) } fun inputCheckAmountAndSelectOkayButton(input: String): CalculatorScreenRobot { return enterTextIntoView(R.id.inputAmount, input) .clickOkOnView(R.id.buttonOkay) } }
17. Screen Robots withRobot(CalculatorScreenRobot::class.java) .inputCheckAmountAndSelectOkayButton("11") .verifyTipIsCorrect("1.98")
18. Screen Robots robot { inputCheckAmountAndSelectOkayButton("11") verifyTipIsCorrect("1.98") }
19. Extension functions
20. https://twitter.com/objcode/status/1123082385090908160
21. Without Extension functions assert(contentViewModel.observeQueueState().value == ContentState.Loading())
22. Extension functions private fun ContentViewModel.hasState(state: ContentState) { assert(observeQueueState().value == state) }
23. Extension functions contentViewModel.hasState(ContentState.Loading())
24. Infix functions
25. https://twitter.com/PreusslerBerlin/status/ 1123107023103696896 https://twitter.com/jossiwolf/status/ 1123039773541707776
26. Without Infix functions fun verifyTipIsCorrect(tip: String) { onView(withId(R.id.textTip)) .check(matches(withText(tip))) }
27. Infix functions infix fun Int.shouldHaveText(expected: String) { onView(withId(this)) .check(matches(withText(expected))) }
28. Infix functions fun verifyTipIsCorrect(tip: String) { R.id.textTip shouldHaveText tip }
29. Combining multiple features inline fun <reified T : ScreenRobot<*>> robot(block: T.() -> Unit) { T::class.java.newInstance().block() } robot<CalculatorScreenRobot> { inputCheckAmountAndSelectOkayButton("11") verifyTipIsCorrect("1.98") }
30. Data classes
31. https://twitter.com/shekibobo/status/ 1123037412328988673 https://twitter.com/tasomaniac/status/ 1123104225196683264
32. Data classes data class UpdateData( var shareMode: ShareMode = ShareMode.ADD_TO_QUEUE, var media: MediaEntity? = null, var extraMedia: Array<MediaEntity>? = null, var retweet: RetweetEntity? = null, @Nullable var scheduledAt: Long? = null, var text: String = "", var facebookText: String = "", var profileIds: List<String>? = null, var subProfileIds: List<String>? = null, var sourceUrl: String? = null, var importId: String? = null, var shareDetails: ShareDetails? = null, var userChangedMedia: Boolean = false, var isEditing: Boolean = false, var editingProfile: ProfileEntity? = null, var networks: List<String>? = null, var facebookTags: List<FacebookTag>? = null, var id: String? = "", var lastEditedDate: Long? = 0, var editingProfileTimezone: String? = null, val location: Location? = null, val commentEnabled: Boolean = false, val commentText: String? = null )
33. Data classes UpdateData(null, null, emptyArray(), null, 0, "Hello World", "", emptyList(), emptyList(), null, "buffer.com", null, false, true, null, emptyList(), null, "", 0, null, null, false, "")
34. Data classes UpdateData(text = "Hello World", sourceUrl = "buffer.com")
35. Lazy property delegation
36. https://twitter.com/POTUS404/status/1123210124108103680
37. private val errorMessage by lazy { DataFactory.randomString() }
38. Example https://youtu.be/wlb3lg5JocA
39. Example https://youtu.be/wlb3lg5JocA
40. Kotlin libraries
41. Kakao
42. https://twitter.com/erafn/status/1123067587125026816
43. Kakao class SearchScreen : Screen<SearchScreen>() { val searchButton = KButton { withId(R.id.searchButton) } val snackbar = KView { withId(com.google.android.material.R.id.snackbar_text) } }
44. Kakao screen { searchButton.click() snackbar.isDisplayed() }
45. Spek
46. Spek class ProfileSpec : Spek({ given("twitter profile") { on("validate image count") { it("should be valid for four images") { } it("should fail for ten images") { } } } })
47. Spek Spek:ProfileSpec:given twitter profile:on validate image count:it 
 should be valid for four images
 => java.lang.AssertionError: Expected <true>, actual <false>.
48. Mockito-Kotlin
49. https://twitter.com/Exallium/status/1123214566052323329
50. Mockito val mockedUpdate = mock(Update::class.java) `when`(mockedUpdate.toString()).thenReturn("Update")
51. Mockito-Kotlin val mockedUpdate = mock<Update> { on { toString() } doReturn "Update" }
52. Kluent
53. Kluent message shouldEqual "hello" message.shouldEqual("hello") message `should equal` "hello"
54. Kluent invoking { read() } shouldThrow IOException::class
55. Kluent Verify on mockedUpdate that mockedUpdate.toString() was called When calling stub.length itReturns 4
56. Biscotti
57. Biscotti verifyActivityLaunched(MainActivity::class.java.name) { onView(withId(R.id.button_faq)) .perform(click()) }
58. https://vgonda.github.io/Talk-Resources/ @TTGonda
59. Thanks! Victoria Gonda victoriagonda.com @TTGonda