android-unit-test

Android Unit Testing Expert

Эксперт по тестированию Android приложений с использованием JUnit 5, Mockito и Kotlin.

Настройка зависимостей

// build.gradle (app) dependencies { // Unit testing testImplementation 'junit:junit:4.13.2' testImplementation 'org.junit.jupiter:junit-jupiter:5.9.3' testImplementation 'org.mockito:mockito-core:5.3.1' testImplementation 'org.mockito.kotlin:mockito-kotlin:5.0.0' testImplementation 'io.mockk:mockk:1.13.5' testImplementation 'org.jetbrains.kotlinx:kotlinx-coroutines-test:1.7.1' testImplementation 'app.cash.turbine:turbine:1.0.0'

// Instrumentation testing
androidTestImplementation 'androidx.test.ext:junit:1.1.5'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.1'
androidTestImplementation 'androidx.test:runner:1.5.2'
androidTestImplementation 'androidx.test:rules:1.5.0'

}

AAA Pattern (Arrange, Act, Assert)

class UserRepositoryTest {

@Test
fun `getUser returns user when found`() {
    // Arrange
    val userId = "user_123"
    val expectedUser = User(userId, "John Doe", "john@example.com")
    val mockDataSource = mock&#x3C;UserDataSource> {
        on { getUser(userId) } doReturn expectedUser
    }
    val repository = UserRepository(mockDataSource)

    // Act
    val result = repository.getUser(userId)

    // Assert
    assertEquals(expectedUser, result)
    verify(mockDataSource).getUser(userId)
}

}

ViewModel Testing

@OptIn(ExperimentalCoroutinesApi::class) class UserViewModelTest {

@get:Rule
val mainDispatcherRule = MainDispatcherRule()

private lateinit var viewModel: UserViewModel
private lateinit var repository: UserRepository

@Before
fun setup() {
    repository = mock()
    viewModel = UserViewModel(repository)
}

@Test
fun `loadUser updates state to success when repository returns user`() = runTest {
    // Arrange
    val user = User("1", "John", "john@example.com")
    whenever(repository.getUser("1")).thenReturn(Result.success(user))

    // Act
    viewModel.loadUser("1")

    // Assert
    val state = viewModel.uiState.value
    assertTrue(state is UserUiState.Success)
    assertEquals(user, (state as UserUiState.Success).user)
}

@Test
fun `loadUser updates state to error when repository fails`() = runTest {
    // Arrange
    val exception = IOException("Network error")
    whenever(repository.getUser("1")).thenReturn(Result.failure(exception))

    // Act
    viewModel.loadUser("1")

    // Assert
    val state = viewModel.uiState.value
    assertTrue(state is UserUiState.Error)
    assertEquals("Network error", (state as UserUiState.Error).message)
}

}

MainDispatcherRule

@OptIn(ExperimentalCoroutinesApi::class) class MainDispatcherRule( private val testDispatcher: TestDispatcher = UnconfinedTestDispatcher() ) : TestWatcher() {

override fun starting(description: Description) {
    Dispatchers.setMain(testDispatcher)
}

override fun finished(description: Description) {
    Dispatchers.resetMain()
}

}

Repository Testing

class UserRepositoryTest {

private lateinit var repository: UserRepository
private lateinit var remoteDataSource: UserRemoteDataSource
private lateinit var localDataSource: UserLocalDataSource

@Before
fun setup() {
    remoteDataSource = mock()
    localDataSource = mock()
    repository = UserRepository(remoteDataSource, localDataSource)
}

@Test
fun `getUsers returns cached data when available`() = runTest {
    // Arrange
    val cachedUsers = listOf(User("1", "John", "john@example.com"))
    whenever(localDataSource.getUsers()).thenReturn(cachedUsers)

    // Act
    val result = repository.getUsers()

    // Assert
    assertEquals(cachedUsers, result)
    verify(localDataSource).getUsers()
    verifyNoInteractions(remoteDataSource)
}

@Test
fun `getUsers fetches from remote when cache is empty`() = runTest {
    // Arrange
    val remoteUsers = listOf(User("1", "John", "john@example.com"))
    whenever(localDataSource.getUsers()).thenReturn(emptyList())
    whenever(remoteDataSource.getUsers()).thenReturn(remoteUsers)

    // Act
    val result = repository.getUsers()

    // Assert
    assertEquals(remoteUsers, result)
    verify(localDataSource).saveUsers(remoteUsers)
}

}

Flow Testing с Turbine

@OptIn(ExperimentalCoroutinesApi::class) class FlowTestExample {

@Test
fun `userFlow emits expected values`() = runTest {
    val repository = UserRepository()

    repository.userFlow.test {
        // Initial state
        assertEquals(UserState.Loading, awaitItem())

        // After loading
        assertEquals(UserState.Success(user), awaitItem())

        // Cancel and ensure no more emissions
        cancelAndIgnoreRemainingEvents()
    }
}

@Test
fun `searchFlow debounces and emits results`() = runTest {
    val viewModel = SearchViewModel()

    viewModel.searchResults.test {
        viewModel.onSearchQueryChanged("test")
        advanceTimeBy(300) // Debounce time

        val result = awaitItem()
        assertTrue(result.isNotEmpty())

        cancelAndIgnoreRemainingEvents()
    }
}

}

Параметризованные тесты

class CalculatorTest {

@ParameterizedTest
@CsvSource(
    "1, 1, 2",
    "2, 3, 5",
    "10, -5, 5",
    "0, 0, 0"
)
fun `add returns correct sum`(a: Int, b: Int, expected: Int) {
    val calculator = Calculator()
    assertEquals(expected, calculator.add(a, b))
}

@ParameterizedTest
@MethodSource("divisionTestData")
fun `divide handles edge cases`(a: Int, b: Int, expected: Result&#x3C;Int>) {
    val calculator = Calculator()
    assertEquals(expected, calculator.divide(a, b))
}

companion object {
    @JvmStatic
    fun divisionTestData() = listOf(
        Arguments.of(10, 2, Result.success(5)),
        Arguments.of(9, 3, Result.success(3)),
        Arguments.of(5, 0, Result.failure&#x3C;Int>(ArithmeticException()))
    )
}

}

MockK для Kotlin

class UserServiceTest {

@MockK
private lateinit var api: UserApi

@MockK
private lateinit var cache: UserCache

private lateinit var service: UserService

@Before
fun setup() {
    MockKAnnotations.init(this)
    service = UserService(api, cache)
}

@Test
fun `getUser uses coEvery for suspend functions`() = runTest {
    // Arrange
    val user = User("1", "John", "john@example.com")
    coEvery { api.getUser("1") } returns user
    coEvery { cache.save(any()) } just Runs

    // Act
    val result = service.getUser("1")

    // Assert
    assertEquals(user, result)
    coVerify { cache.save(user) }
}

@Test
fun `verify call order`() = runTest {
    val user = User("1", "John", "john@example.com")
    coEvery { api.getUser("1") } returns user
    coEvery { cache.save(any()) } just Runs

    service.getUser("1")

    coVerifyOrder {
        api.getUser("1")
        cache.save(user)
    }
}

}

Test Data Factories

object UserFactory { fun create( id: String = "user_${UUID.randomUUID()}", name: String = "Test User", email: String = "test@example.com", isActive: Boolean = true ) = User(id, name, email, isActive)

fun createList(count: Int = 5) = (1..count).map {
    create(id = "user_$it", name = "User $it")
}

}

// Usage in tests @Test fun test with factory() { val user = UserFactory.create(name = "Custom Name") val users = UserFactory.createList(10) }

Custom Assertions

fun <T> Result<T>.shouldBeSuccess(): T { assertTrue(this.isSuccess, "Expected success but was failure: ${this.exceptionOrNull()}") return this.getOrThrow() }

fun <T> Result<T>.shouldBeFailure(): Throwable { assertTrue(this.isFailure, "Expected failure but was success: ${this.getOrNull()}") return this.exceptionOrNull()!! }

// Usage @Test fun repository returns success() { val result = repository.getUser("1") val user = result.shouldBeSuccess() assertEquals("John", user.name) }

Espresso UI Testing

@RunWith(AndroidJUnit4::class) class LoginActivityTest {

@get:Rule
val activityRule = ActivityScenarioRule(LoginActivity::class.java)

@Test
fun loginButton_isDisabled_whenEmailIsEmpty() {
    onView(withId(R.id.emailInput)).perform(clearText())
    onView(withId(R.id.passwordInput)).perform(typeText("password123"))

    onView(withId(R.id.loginButton)).check(matches(not(isEnabled())))
}

@Test
fun successfulLogin_navigatesToHome() {
    onView(withId(R.id.emailInput)).perform(typeText("test@example.com"))
    onView(withId(R.id.passwordInput)).perform(typeText("password123"))
    onView(withId(R.id.loginButton)).perform(click())

    onView(withId(R.id.homeScreen)).check(matches(isDisplayed()))
}

}

Лучшие практики

Один тест = одно поведение — каждый тест проверяет одну вещь
Описательные имена — используйте backticks для читаемых названий
AAA паттерн — Arrange, Act, Assert в каждом тесте
Изолированность — тесты не зависят друг от друга
Быстрота — unit тесты должны выполняться мгновенно
Тестируйте edge cases — null, пустые списки, ошибки

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