Android Testing

Android Testing Strategies

This skill provides expert guidance on testing modern Android applications, inspired by "Now in Android". It covers Unit Tests, Hilt Integration Tests, and Screenshot Testing.

Testing Pyramid

1. Unit Tests: Fast, isolate logic (ViewModels, Repositories).
2. Integration Tests: Test interactions (Room DAOs, Retrofit vs MockWebServer).
3. UI/Screenshot Tests: Verify UI correctness (Compose).

Dependencies (libs.versions.toml)

Ensure you have the right testing dependencies.

[libraries]junit4 = { module = "junit:junit", version = "4.13.2" }kotlinx-coroutines-test = { group = "org.jetbrains.kotlinx", name = "kotlinx-coroutines-test", version.ref = "kotlinxCoroutines" }androidx-test-ext-junit = { group = "androidx.test.ext", name = "junit", version = "1.1.5" }espresso-core = { group = "androidx.test.espresso", name = "espresso-core", version = "3.5.1" }compose-ui-test = { group = "androidx.compose.ui", name = "ui-test-junit4" }hilt-android-testing = { group = "com.google.dagger", name = "hilt-android-testing", version.ref = "hilt" }roborazzi = { group = "io.github.takahirom.roborazzi", name = "roborazzi", version.ref = "roborazzi" }

Screenshot Testing with Roborazzi

Screenshot tests ensure your UI doesn't regress visually. NiA uses Roborazzi because it runs on the JVM (fast) without needing an emulator.

Setup

1. Add the plugin to libs.versions.toml:
   toml

   [plugins]roborazzi = { id = "io.github.takahirom.roborazzi", version.ref = "roborazzi" }

2. Apply it in your module's build.gradle.kts:
   kotlin

   plugins {    alias(libs.plugins.roborazzi)}

Writing a Screenshot Test

@RunWith(AndroidJUnit4::class)@GraphicsMode(GraphicsMode.Mode.NATIVE)@Config(sdk = [33], qualifiers = RobolectricDeviceQualifiers.Pixel5)class MyScreenScreenshotTest {
    @get:Rule    val composeTestRule = createAndroidComposeRule<ComponentActivity>()
    @Test    fun captureMyScreen() {        composeTestRule.setContent {            MyTheme {                MyScreen()            }        }
        composeTestRule.onRoot()            .captureRoboImage()    }}

Hilt Testing

Use HiltAndroidRule to inject dependencies in tests.

@HiltAndroidTestclass MyDaoTest {
    @get:Rule    var hiltRule = HiltAndroidRule(this)
    @Inject    lateinit var database: MyDatabase    private lateinit var dao: MyDao
    @Before    fun init() {        hiltRule.inject()        dao = database.myDao()    }        // ... tests}

Running Tests

• Unit: ./gradlew test
• Screenshots: ./gradlew recordRoborazziDebug (to record) / ./gradlew verifyRoborazziDebug (to verify)