android-kotlin-testing

name	android-kotlin-testing
description	Android testing patterns — ViewModel unit tests with Turbine, Compose UI semantics, Hilt TestInstallIn fakes, coroutine test dispatchers, and release quality gates. Use when writing tests, setting up CI, mocking repositories, or asking "how to test ViewModel", "Compose UI test", "Turbine StateFlow".

Android Kotlin — Testing Module

Parent kit: ../../SKILL.md · Index: ../../AGENTS.md

Read First

File	When
../../references/11-testing.md	Turbine, fakes, Compose test tags
../../references/05-hilt-di.md	TestInstallIn modules
../../references/13-release-checklist.md	Pre-ship checklist

ViewModel Test Template

@OptIn(ExperimentalCoroutinesApi::class)
class FeatureViewModelTest {

    @get:Rule
    val mainDispatcherRule = MainDispatcherRule()

    private val fakeRepo = FakeFeatureRepository()
    private lateinit var viewModel: FeatureViewModel

    @Before
    fun setup() {
        viewModel = FeatureViewModel(fakeRepo)
    }

    @Test
    fun `refresh success clears loading`() = runTest {
        fakeRepo.syncResult = Result.success(Unit)

        viewModel.onEvent(FeatureUiEvent.Refresh)

        viewModel.state.test {
            skipItems(1)
            val loading = awaitItem()
            assertTrue(loading.isLoading)
            val done = awaitItem()
            assertFalse(done.isLoading)
            assertNull(done.error)
        }
    }
}

Fake Over Mock

class FakeFeatureRepository : FeatureRepository {
    var syncResult: Result<Unit> = Result.success(Unit)
    private val items = MutableStateFlow<List<Feature>>(emptyList())

    override fun observeItems(): Flow<List<Feature>> = items
    override suspend fun sync(): Result<Unit> = syncResult
}

Prefer fakes implementing real interfaces — tests behavior, not interaction order.

Compose UI Test

class FeatureScreenTest {
    @get:Rule
    val composeRule = createComposeRule()

    @Test
    fun showsEmptyState() {
        composeRule.setContent {
            AppTheme {
                FeatureContent(
                    state = FeatureUiState(items = emptyList()),
                    onEvent = {}
                )
            }
        }
        composeRule.onNodeWithTag("feature_empty").assertIsDisplayed()
    }
}

Test stateless FeatureContent, not ViewModel-integrated screen.

What to Test vs Skip

Always test	Usually skip
ViewModel state transitions	Room generated SQL
Repository mappers	Hilt graph wiring (compile-time)
Error paths (Result.failure)	Pixel-perfect screenshots
Critical user flows (instrumented)	Third-party SDK internals

CI Gate

Repo skill validation must pass before merge:

python3 scripts/validate_skills.py --strict