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)

android-testing