The Future of Writing Tests for Jetpack Compose in Android

There are no hard and fast rules about how much and how to test a component. In my talk, I'll show you how to start using Test Driven Development for an Android app using Jetpack compose.
When using the TDD approach, one begins writing the addition tests before the implementation code.

Transcript

1. Android Speaker Image Placeholder The Future of Writing Tests for Jetpack Compose in Android Hannah Olukoye
2. About Me
3. How to Test Writing the tests What to Test Questions?? 1 3 2 4 Today's Agenda
4. Test Driven Development (TDD) Red Refactor Green
5. Example: Display a list of items
6. ★ The list is empty ★ The list is not empty ★ Verify if an item in the list is a text What to test?
7. RecyclerView vs LazyColumn Jetpack Compose
8. ★ LazyColumn Parameters Writing tests modifier: state: contentPadding: reverseLayout: verticalArrangement: horizontalAlignment: flingBehavior: userScrollEnabled: content:
9. val tagDescTest = "LazyColumnItemTest" @RunWith(AndroidJUnit4::class) class LazyColumnTest { @get:Rule val composeTestRule = createComposeRule() @Test fun lazyColumnTestBackgroundColour() { composeTestRule.setContent { Surface(color = MaterialTheme.colors.background) { LazyColumn( modifier = Modifier.testTag(tagDescTest), flingBehavior = ScrollableDefaults.flingBehavior() ) { items(1) { index -> Text(text = "Item: $index") } } } } }
10. Run the test on Android Studio
11. Failed test
12. Passed test
13. val tagDescTest = "LazyColumnItemTest" @RunWith(AndroidJUnit4::class) class LazyColumnTest { @get:Rule val composeTestRule = createComposeRule() @Test fun lazyColumnTestBackgroundColour() { composeTestRule.setContent { Surface(color = MaterialTheme.colors.background) { LazyColumn( modifier = Modifier.testTag(tagDescTest), flingBehavior = ScrollableDefaults.flingBehavior() ) { items(1) { index -> Text(text = "Item: $index") } } } } }
14. Implementation - Definition data class Demo(val description: String) val demo = listOf( Demo("Item 1"), Demo("Item 2"), Demo("Item 3"), Demo("Item 4") ) class MainActivity : ComponentActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContent { DisplayList(demo = demo) DummyApp() } } }
15. Implementation - Integration @Preview @Composable fun DummyApp() { DisplayList(demo = demo) } @Composable fun DisplayList(demo: List<Demo>) { Surface(color = MaterialTheme.colors.background) { LazyColumn(modifier = Modifier.testTag(description_tag), flingBehavior = ScrollableDefaults .flingBehavior() ) { items(demo) { demo -> Text(text = demo.description) } } } }
16. Preview
17. Resources • https://developer.android.com/codelabs/jetpack-compose-basics • https://www.wwt.com/article/test-driven-development-with-android • https://blog.canopas.com/how-to-use-tdd-effectively-to-write-android-integration-tests-5e fc7ee48ba8 • https://paulallies.medium.com/getting-started-with-tdd-kotlin-and-jetpack-compose-887c 04d733f9
18. Thank you! Twitter: @hannah_omu