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

• Unit Tests: Fast, isolate logic (ViewModels, Repositories).

• Integration Tests: Test interactions (Room DAOs, Retrofit vs MockWebServer).

• 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

• Add the plugin to libs.versions.toml : [plugins] roborazzi = { id = "io.github.takahirom.roborazzi", version.ref = "roborazzi" }

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

@HiltAndroidTest class 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)