Android Testing Guide

JUnit5, MockK, Turbine, Compose UI Testing을 사용한 테스트 가이드입니다.

Testing Stack

Type	Framework	Purpose
Unit	JUnit5 + MockK	ViewModel, UseCase, Repository
Flow	Turbine	StateFlow, Channel testing
Coroutines	kotlinx-coroutines-test	runTest, advanceUntilIdle
UI	Compose Testing	Composable rendering, interaction
Integration	Hilt Testing	DI integration

Coverage Target

• Overall: 80%+
• Domain Layer: 90%+ (pure business logic)
• Presentation Layer: 70%+ (ViewModel, state logic)
• Data Layer: 60%+ (repository, mapper)

Quick Test Commands

# All tests
./gradlew test

# Module tests
./gradlew :feature:home:testDebugUnitTest
./gradlew :core:domain:test

# With coverage
./gradlew testDebugUnitTestCoverage

# Single test class
./gradlew test --tests "*.HomeViewModelTest"

Test Templates

테스트 함수 이름은 되도록 한국어로 작성 해주세요.

ViewModel Test

ViewModel 테스트는 state 변화와 effect 발생을 검증합니다.

상세 템플릿: templates/viewmodel-test.md

UseCase Test

UseCase 테스트는 비즈니스 로직과 repository 호출을 검증합니다.

상세 템플릿: templates/usecase-test.md

Compose UI Test

Compose 테스트는 UI 렌더링과 사용자 상호작용을 검증합니다.

상세 템플릿: templates/compose-test.md

Test Naming Convention

// Pattern: `given_when_then` or `should_when`
@Test
fun `loadData should update state with results when useCase succeeds`()

@Test
fun `should show error message when loading fails`()

@Test
fun `given empty list when render then show empty state`()

Common Test Setup

Dependencies (build.gradle.kts)

testImplementation("org.junit.jupiter:junit-jupiter:5.10.0")
testImplementation("io.mockk:mockk:1.13.8")
testImplementation("app.cash.turbine:turbine:1.0.0")
testImplementation("org.jetbrains.kotlinx:kotlinx-coroutines-test:1.7.3")
testImplementation("androidx.compose.ui:ui-test-junit4")
debugImplementation("androidx.compose.ui:ui-test-manifest")

Test Rule Setup

@ExtendWith(MockKExtension::class)
class ViewModelTest {

    @MockK
    private lateinit var useCase: SomeUseCase

    @MockK
    private lateinit var repository: SomeRepository

    private lateinit var viewModel: SomeViewModel

    @BeforeEach
    fun setup() {
        viewModel = SomeViewModel(useCase)
    }

    @AfterEach
    fun tearDown() {
        clearAllMocks()
    }
}

Best Practices

DO

• Test behavior, not implementation
• Use meaningful test names
• One assertion per test (when possible)
• Test edge cases and error scenarios
• Use Turbine for Flow testing

DON'T

• Test private methods directly
• Mock everything (test real logic when possible)
• Write flaky tests
• Skip error case testing
• Use Thread.sleep() (use advanceUntilIdle)