build.gradle.kts

    dependencies {
        implementation("androidx.datastore:datastore-preferences:1.0.0")
        testImplementation("org.jetbrains.kotlinx:kotlinx-coroutines-test:1.6.4")
        ...
    }

UserRepository.kt

val KEY_NAME = stringPreferencesKey("name")

class UserRepository(
    private val dataStore: DataStore<Preferences>,
) {
    val name: Flow<String> = dataStore.data.map { preferences ->
        preferences[KEY_NAME].orEmpty()
    }

    suspend fun setName(name: String) {
        dataStore.edit { mutablePreferences ->
            mutablePreferences[KEY_NAME] = name
        }
    }
}

UserRepositoryTest.kt

class UserRepositoryTest {

    @get:Rule
    val tmpFolder: TemporaryFolder = TemporaryFolder.builder().assureDeletion().build()
    private val testDispatcher = UnconfinedTestDispatcher()
    private val testScope = TestScope(testDispatcher + Job())

    private val testDataStore: DataStore<Preferences> = PreferenceDataStoreFactory.create(
        scope = testScope,
        produceFile = { tmpFolder.newFile("user.preferences_pb") }
    )
    private val subject: UserRepository = UserRepository(testDataStore)

    @Test
    fun whenGetNameForTheFirstTime_thenReturnDefaultValue() = testScope.runTest {
        //When
        val actual = subject.name.first()

        //Then
        assertEquals("", actual)
    }

    @Test
    fun whenSetName_thenUpdateName() = testScope.runTest {
        // When
        subject.setName("Alfian")

        //Then
        assertEquals("Alfian", subject.name.first())
    }
}