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

bash

# 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

kotlin

// 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)

kotlin

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

kotlin

@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)