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
<
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 funloadUser 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 fungetUsers 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 fungetUsers 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 funuserFlow 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 funsearchFlow 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" ) funadd returns correct sum( a : Int , b : Int , expected : Int ) { val calculator = Calculator ( ) assertEquals ( expected , calculator . add ( a , b ) ) } @ParameterizedTest @MethodSource ( "divisionTestData" ) fundivide handles edge cases( a : Int , b : Int , expected : Result < 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 < 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 funverify 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 funtest with factory( ) { val user = UserFactory . create ( name = "Custom Name" ) val users = UserFactory . createList ( 10 ) } Custom Assertions fun < TResult < 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