The Importance of Being Tested

Slides of the talk I gave at Droidcon Berlin 2021

1. Roberto Orgiu | Senior Android Engineer @ NYTimes | @_tiwiz The importance of being tested
2. What is testing about?
3. Correctness Functioning
4. Is everything testable?
5. class Repository { private val dep = Dependency( ) fun fetch() = dep.getData( ) }
6. class Repository ( private val dep: Dependenc y ) { fun fetch() = dep.getData( ) }
7. What should I test?
8. Test the logic, not the code. Fabio Collini (probably?)
9. fun testCode() { repository.fetch( ) verify(mockDependency).getData( ) }
10. fun testLogic() { val actualResult = repository.fetch( ) verify(actualResult ) .isEqualTo(expectedResult ) }
11. Was that unit testing?
12. Was that unit testing? Is unit testing enough?
13. cwti.link/twitch
14. What about integration testing?
15. What about integration testing? integration tests validate the collaboration and interaction of a group of units.
16. My take on integration testing
17. My take on integration testing •No Android deps •Test fl ow from start to end •Use Robolectric
18. class RootFragment : Fragment() { lateinit var repository: Repositor y lateinit var view: Vie w fun onResume() { val response = repository.fetchThings( ) view.bindResults(response ) } }
19. class IntegrationTest { private val mock = TestDouble(Service() ) private val testFragment = RootFragment( ) fun integrationTest() { run(testFragment).verify( ) } } androidTest
20. What about Network?
21. What about network? Network is unreliable
22. What about network? • Retro fi t + OkHttp + MockWebServer • Ktor + MockEngine
23. val retrofit = Retrofit.Builder( ) .baseUrl("https://api.github.com/" ) .build( ) This should come from the outside!
24. val retrofit = Retrofit.Builder( ) .baseUrl(url ) .build( )
25. val server = MockWebServer( ) server.enqueue ( MockResponse().setBody("hello, world!" ) ) server.start( ) val url = server.url( )
26. HttpClient(Android) { install(Logging) { … } install(JsonFeature) { … } } This should come from the outside!
27. val mockEngine = MockEngine { request - > respond ( content = ByteReadChannel(content) , status = HttpStatusCode.OK , headers = headersOf(ContentType, type ) ) }
28. What about UI testing?
29. What about UI testing?
30. @get:Rule var activityScenarioRule = activityScenarioRule<MyActivity>( ) @Tes t fun changeText() { onView(withId(startViewId) ) .perform ( typeText(MESSAGE) , closeSoftKeyboard( ) ) onView(withId(buttonViewId) ) .perform(click() ) onView(withId(targetView) ) .check(matches(withText(MESSAGE)) ) }
33. @Composabl e fun SimpleUI() { var clicks by remember { mutableStateOf(0) } Column { Button ( onClick = { clicks++ } ) { Text(text = "Click me" ) } if (clicks > 0) { Text(text = "$clicks" ) } } }
34. @get:Rul e val composeTestRule = createComposeRule( ) @Tes t fun verify_initial_case() { composeTestRule.setContent { SimpleUI( ) } composeTestRule.onNodeWithTag("clicks" ) .assertDoesNotExist( ) }
35. @get:Rul e val composeTestRule = createComposeRule( ) @Tes t fun verify_last_case() { composeTestRule.setContent { SimpleUI( ) } composeTestRule.onNodeWithText("Click me" ) .performClick( ) with(composeTestRule.onNodeWithTag("clicks")) { assertIsDisplayed( ) assertTextEquals("1" ) } }
36. How can I start testing?
37. Roberto Orgiu | Senior Android Engineer @ NYTimes | @_tiwiz Thanks for listening. Q&A Time