easydev991/testing

Testing

When to Use

• Use this skill when writing unit tests for business logic (ViewModels, Use Cases, Domain models)
• Use this skill when writing integration tests for DAO and Repository
• Use this skill when writing UI tests for Compose components
• Use this skill when testing network functions (only on mocks)
• Use this skill when testing Flow/StateFlow using Turbine
• Use this skill when you need to test exception handling in coroutines
• This skill is useful when choosing the right type of test for a specific scenario
• This skill helps determine when to use unit tests with mocks vs integration tests

Test Types

• Unit: business logic in isolation, MockK for dependencies, AAA pattern
• Integration: interaction between layers (DAO, Repository), real DB implementations
• UI: critical scenarios, Compose Testing for components

Tools

• JUnit 5 - unit tests
• MockK - mocking
• Compose Testing - Compose components
• Room Testing - for DB integration tests
• kotlinx-coroutines-test - for coroutine testing
• Turbine - for Flow/StateFlow testing (app.cash.turbine:turbine:1.1.0)

Running Tests and Reports

make test command

Use the make test command to run all unit tests:

make test

This command:

1. Runs ./gradlew test --console=plain - all unit tests (JVM, without device)
2. Automatically executes scripts/test_report.py script after test completion
3. Shows detailed report with statistics by test classes

test_report.py script

The scripts/test_report.py script generates a detailed test results report:

• Shows overall statistics: total tests, passed, failed
• Lists all failed tests with class and method names
• Displays statistics table by test classes (total, failed, passed)
• Sorts classes by number of failed tests (descending)
• Uses colors for easy reading (green for success, red for errors)
• Returns exit code 0 if all tests passed, 1 if there are failures

Example script output:

================================================================================
✅ BUILD SUCCESSFUL
================================================================================

Test Statistics:
Total tests: 145
✅ Passed: 142
❌ Failed: 3
❌ List of failed tests:
  - AuthViewModelTest::login_withInvalidCredentials_returnsError
  - EventsViewModelTest::loadEvents_whenNetworkError_returnsError
  - ParksRepositoryImplTest::getParks_whenEmpty_returnsEmptyList

================================================================================
Statistics by test classes (5 classes):
================================================================================
Class                                          Failed  Passed  Total
----------------------------------------------------------------------------
AuthViewModelTest                                  1      12       13
EventsViewModelTest                                1       8        9
ParksRepositoryImplTest                            1      15       16
================================================================================

Other Testing Commands

• make android-test - run integration tests on Android device
• make test-all - run all tests (unit + integration)
• make android-test-report - open HTML integration test report in browser

Structure

• app/src/test/ - unit tests (ViewModels, Use Cases, Domain models)
• app/src/androidTest/ - integration/UI tests (DAO, Repository, UI components)
• Structure mirrors code
• Class names: *Test

Best Practices

Important: Recommendations for ViewModel integration tests

• Recommended: Test ViewModels via unit tests with MockK in test/
• Possible (but not recommended): Integration tests for ViewModels in androidTest/ using runTest, MainDispatcherRule, and Turbine
• Acceptable: Integration tests for components with Android API (e.g., CryptoManager with Android Keystore)
• Acceptable: UI tests for Compose components without business logic

Why unit tests with MockK are preferred:

• Faster execution (no real Repository/DB needed)
• More stable and isolated
• In Jetpack-WorkoutApp all ViewModels are tested via unit tests (AuthViewModelTest, EventsViewModelTest)

When to use ViewModel integration tests:

• Only if you need to test integration with real Repository/DB
• Not currently used in JetpackWorkoutApp, but technically possible

Working Testing Approach

Unit Tests for ViewModels (with MockK)

Important: ViewModels using viewModelScope.launch require MainDispatcherRule in tests. viewModelScope runs on Dispatchers.Main, which is not configured by default in Unit tests. Without MainDispatcherRule, coroutines won't be able to start, and state checks will be incorrect.

Creating MainDispatcherRule:

@ExperimentalCoroutinesApi
class MainDispatcherRule(
    private val testDispatcher: TestDispatcher = StandardTestDispatcher()
) : TestWatcher() {
    override fun starting(description: Description) {
        Dispatchers.setMain(testDispatcher)
    }

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

Example unit test:

@ExperimentalCoroutinesApi
class AuthViewModelTest {
    @get:Rule
    val mainDispatcherRule = MainDispatcherRule()

    private lateinit var viewModel: AuthViewModel
    private val loginUseCase: LoginUseCase = mockk()

    @Before
    fun setup() {
        viewModel = AuthViewModel(loginUseCase)
    }

    @Test
    fun login_whenValidCredentials_thenReturnsSuccess() = runTest {
        // Given
        val credentials = LoginCredentials("[email protected]", "password")
        coEvery { loginUseCase(credentials) } returns Result.success(loginSuccess)

        // When
        viewModel.login()
        advanceUntilIdle()

        // Then
        assertTrue(viewModel.uiState.value is LoginUiState.Idle)
    }
}

Integration Tests for DAO and Repository

Use real in-memory database for DAO tests:

@RunWith(AndroidJUnit4::class)
class ParksDaoTest {
    private lateinit var database: AppDatabase
    private lateinit var parksDao: ParksDao

    @Before
    fun createDb() {
        database = Room.inMemoryDatabaseBuilder(
            ApplicationProvider.getApplicationContext(),
            AppDatabase::class.java
        ).allowMainThreadQueries().build()
        parksDao = database.parksDao()
    }

    @After
    @Throws(IOException::class)
    fun closeDb() {
        database.close()
    }

    @Test
    fun insertAndGetPark() = runTest {
        // Given
        val park = ParkEntity(/* ... */)

        // When
        parksDao.insert(park)
        val loaded = parksDao.getById(park.id)

        // Then
        assertEquals(park, loaded)
    }
}

UI Tests for Compose Components

@RunWith(AndroidJUnit4::class)
class LoginScreenTest {
    @get:Rule
    val composeTestRule = createComposeRule()

    @Test
    fun loginScreen_showsEmailField() {
        composeTestRule.setContent {
            LoginScreen()
        }

        composeTestRule
            .onNodeWithText("Email")
            .assertIsDisplayed()
    }
}

Testing Network Functions

• Only on mocks: Use MockK for API clients (SWApi, Retrofit)
• No real requests: Real HTTP requests to server are prohibited in tests
• Isolated testing: Test business logic independently of network
• Predictable responses: Use fixed mock server responses

Mock example:

@Test
fun loadParks_whenSuccess_thenReturnsParks() = runTest {
    // Given
    val mockParks = listOf(Park(/* ... */))
    coEvery { api.getParks() } returns Response.success(mockParks)

    // When
    val result = repository.getParks()

    // Then
    assertEquals(mockParks, result)
}

Mocking HttpException:

@Test
fun loadParks_whenNetworkError_thenReturnsError() = runTest {
    // Given
    val httpException = HttpException(
        Response.error<Any>(404, "Not found".toResponseBody())
    )
    coEvery { api.getParks() } throws httpException

    // When
    val result = repository.getParks()

    // Then
    assertTrue(result.isFailure)
}

Testing Flow with Exceptions

Important: For Flows with exceptions handled via catch, use first() or collect() instead of Turbine.

Testing IOException (handled in catch):

@Test
fun loadData_whenIOException_thenReturnsErrorState() = runTest {
    // Given
    coEvery { repository.getData() } throws IOException("Network error")

    // When
    val result = useCase().first()

    // Then
    assertTrue(result.isFailure)
}

Testing other exceptions (propagated):

@Test(expected = IllegalStateException::class)
fun loadData_whenIllegalState_thenThrows() = runTest {
    // Given
    coEvery { repository.getData() } throws IllegalStateException()

    // When
    useCase().first()
}

Mocking Android Log:

@Before
fun setup() {
    mockkStatic(Log::class)
    every { Log.d(any(), any()) } returns 0
    every { Log.e(any(), any()) } returns 0
}

General Practices

• Fast and independent tests
• Descriptive names
• One test - one assertion
• Test behavior, not implementation
• Integration tests only for DAO and Repository
• Unit tests for ViewModels with mocks
• Network functions only on mocks (no real requests)
• UI tests for Compose components without business logic
• Use JUnit 5 annotations (@Test, @Before, @After)
• Use JUnit 5 assertions (assertEquals, assertTrue, assertNull)