:core:testing

Shared JVM test helpers for repositories and ViewModels: MainDispatcherRule, FakeUserPreferencesDataSource, and FakeAuthDataSource.

Add the helpers

Add this to the consuming module’s build.gradle.kts:

dependencies {
    testImplementation(projects.core.testing)
}

The Android convention supplies the generic test stack; these shared helpers are opt-in. This module re-exports JUnit4, Kotlin test, coroutine test, Turbine and Truth to its test consumers.

The auth fake’s sign-in/registration operations throw UnsupportedOperationException, including email/password operations. This is a limitation of this fake, not a restriction on all JVM tests. Use a suitable test double when testing other auth paths.

Test repository success and failure

This complete example belongs under data/src/test/kotlin/dev/atick/data/repository/settings/. It uses the same implementation and assertions as SettingsRepositoryImplTest. No Hilt test graph, Firebase connection or dispatcher replacement is needed for these two suspend repository calls.

package dev.atick.data.repository.settings

import com.google.common.truth.Truth.assertThat
import dev.atick.core.preferences.model.DarkThemeConfigPreferences
import dev.atick.core.testing.data.FakeAuthDataSource
import dev.atick.core.testing.data.FakeUserPreferencesDataSource
import dev.atick.data.model.settings.DarkThemeConfig
import kotlinx.coroutines.test.runTest
import org.junit.Test

class SettingsRepositoryExampleTest {
    private val preferences = FakeUserPreferencesDataSource()
    private val auth = FakeAuthDataSource()
    private val repository = SettingsRepositoryImpl(auth, preferences)

    @Test
    fun `theme update writes preferences`() = runTest {
        val result = repository.setDarkThemeConfig(DarkThemeConfig.LIGHT)

        assertThat(result.isSuccess).isTrue()
        assertThat(preferences.current.darkThemeConfigPreferences)
            .isEqualTo(DarkThemeConfigPreferences.LIGHT)
    }

    @Test
    fun `sign out returns the source failure`() = runTest {
        val failure = IllegalStateException("network down")
        auth.signOutError = failure

        val result = repository.signOut()

        assertThat(result.isFailure).isTrue()
        assertThat(result.exceptionOrNull()).isSameInstanceAs(failure)
    }
}

Run ./gradlew :data:testDebugUnitTest --tests 'dev.atick.data.repository.settings.SettingsRepositoryImplTest' for the existing reference suite. If you add the example class, select SettingsRepositoryExampleTest instead. The existing suite also collects settings with Turbine and checks preference reset ordering.

For ViewModels using viewModelScope, install the rule:

@get:org.junit.Rule
val mainDispatcherRule = dev.atick.core.testing.rule.MainDispatcherRule()

Collect shared state before asserting emitted updates; reading StateFlow.value alone does not start a WhileSubscribed upstream. The default eager dispatcher does not exercise queued overlap; use a controlled dispatcher and suspended operations for concurrency tests.

Further guidance

• State Management — Testing — ViewModel example and state/event contract suites

• Guide — Testing — constructing repository and ViewModel tests

• Architecture — Testing — convention test setup

• Settings repository tests — executable success, failure, Flow and reset-order examples