UseCase Mocking

Android only

The utilities described on this page are provided by the cr-usecases-test module and are available on Android only. For KMP projects, see KMP alternatives below.

The cr-usecases-test module provides mock extensions for use cases. Since execute is a context parameter extension (not a regular method on the use case), standard MockK mocking won't work — the helpers work by mocking build() directly instead. Use the provided utilities.

Dependency

testImplementation("app.futured.arkitekt:cr-usecases-test:6.0.0-beta05")

UseCase Mocking

val mockLoginUseCase: LoginUseCase = mockk()

// Mock with specific args
mockLoginUseCase.mockExecute(args = LoginData("John", "Doe")) { user }

// Mock with any args
mockLoginUseCase.mockExecute { user }

// Mock with nullable args
mockLoginUseCase.mockExecuteNullable(args = null) { user }
mockLoginUseCase.mockExecuteNullable { user }

FlowUseCase Mocking

val mockObserveUseCase: ObserveUserUseCase = mockk()

// Mock with specific args
mockObserveUseCase.mockExecute(args = Unit) { flowOf("John Doe") }

// Mock with any args
mockObserveUseCase.mockExecute { flowOf("John Doe") }

Full Test Example

class FormViewModelTest : ViewModelTest() {

    private val mockSaveUseCase: SaveFormUseCase = mockk()
    private val mockObserveUseCase: ObserveFormUseCase = mockk()
    private lateinit var viewState: FormViewState
    private lateinit var viewModel: FormViewModel

    @Before
    fun setUp() {
        viewState = FormViewState()
        mockObserveUseCase.mockExecute { flowOf("Alice" to "Smith") }
        mockSaveUseCase.mockExecute { "Alice" to "Smith" }
        viewModel = spyk(
            FormViewModel(mockSaveUseCase, mockObserveUseCase, viewState),
            recordPrivateCalls = true,
        ).also {
            every { it.getWorkerDispatcher() } returns Dispatchers.Main
        }
    }
}

This pattern ensures all use cases execute synchronously on the test dispatcher and return predictable results.

KMP Alternatives

On KMP, use cases are plain interfaces, so the preferred approach is writing fakes — simple in-test implementations that return controlled results without any mocking framework.

class FakeLoginUseCase : LoginUseCase {
    var result: User = User("John", "Doe")

    override fun build(args: LoginData): User = result
}

If you prefer a mocking framework, Mokkery supports Kotlin Multiplatform and can mock interfaces across all targets.

val mockLoginUseCase = mock<LoginUseCase>()

everySuspend { mockLoginUseCase.build(any()) } returns user

Refer to the Mokkery documentation for setup and full API reference.