android-kotlin-testing

---
name: android-kotlin-testing
description: >
license: MIT
---

# Android Kotlin — Testing Module

Parent kit: [`../../SKILL.md`](../../SKILL.md) · Index: [`../../AGENTS.md`](../../AGENTS.md)

## Read First

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

## ViewModel Test Template

```kotlin
@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

```kotlin
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

```kotlin
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:

```bash
python3 scripts/validate_skills.py --strict
```