Add test dispatchers

This adds a test implementation of dispatchers with an injected TestDispatcher.
The normal IO dispatcher is automatically swapped out via a TestInstallsIn in core-testing.

This update also updates DataStore to use an injected dispatcher, which allows removing the waitUntil in the navigation tests because we can eagerly read from disk with runTest.

Change-Id: I82abb8c8a57c2beed5ef37bf1e252acf379278cd

app/src/androidTest/java/com/google/samples/apps/nowinandroid/ui/NavigationTest.kt

@@ -17,7 +17,6 @@
 package com.google.samples.apps.nowinandroid.ui
 
 import androidx.compose.ui.test.assertIsOn
-import androidx.compose.ui.test.hasText
 import androidx.compose.ui.test.junit4.createAndroidComposeRule
 import androidx.compose.ui.test.onNodeWithContentDescription
 import androidx.compose.ui.test.onNodeWithText
@@ -84,8 +83,6 @@ class NavigationTest {
     @Test
     fun firstScreen_isForYou() {
         composeTestRule.apply {
-            // WAIT for initial content to be shown
-            waitUntil { onAllNodes(hasText("HEADLINES")).fetchSemanticsNodes().isNotEmpty() }
             // VERIFY first topic is displayed
             onNodeWithText("HEADLINES").assertExists()
         }
@@ -101,8 +98,6 @@ class NavigationTest {
     @Test
     fun navigationBar_navigateToPreviouslySelectedTab_restoresContent() {
         composeTestRule.apply {
-            // WAIT for initial content to be shown
-            waitUntil { onAllNodes(hasText("HEADLINES")).fetchSemanticsNodes().isNotEmpty() }
             // GIVEN the user follows a topic
             onNodeWithText("HEADLINES").performClick()
             // WHEN the user navigates to the Topics destination
@@ -120,8 +115,6 @@ class NavigationTest {
     @Test
     fun navigationBar_reselectTab_keepsState() {
         composeTestRule.apply {
-            // WAIT for initial content to be shown
-            waitUntil { onAllNodes(hasText("HEADLINES")).fetchSemanticsNodes().isNotEmpty() }
             // GIVEN the user follows a topic
             onNodeWithText("HEADLINES").performClick()
             // WHEN the user taps the For You navigation bar item
@@ -179,8 +172,6 @@ class NavigationTest {
     @Test
     fun navigationBar_backFromAnyDestination_returnsToForYou() {
         composeTestRule.apply {
-            // WAIT for initial content to be shown
-            waitUntil { onAllNodes(hasText("HEADLINES")).fetchSemanticsNodes().isNotEmpty() }
             // GIVEN the user navigated to the Episodes destination
             onNodeWithText(episodes).performClick()
             // and then navigated to the Topics destination

core-common/build.gradle

@@ -16,6 +16,7 @@
 plugins {
     id 'com.android.library'
     id 'kotlin-android'
+    id 'kotlin-kapt'
 }
 
 android {
@@ -32,4 +33,10 @@ android {
     kotlinOptions {
         jvmTarget = '1.8'
     }
+}
+
+dependencies {
+    implementation libs.kotlinx.coroutines.android
+    implementation libs.hilt.android
+    kapt libs.hilt.compiler
 }

core-common/src/main/java/com/google/samples/apps/nowinandroid/core/network/NiaDispatchers.kt

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.samples.apps.nowinandroid.core.network
+
+import javax.inject.Qualifier
+import kotlin.annotation.AnnotationRetention.RUNTIME
+
+@Qualifier
+@Retention(RUNTIME)
+annotation class Dispatcher(val niaDispatcher: NiaDispatchers)
+
+enum class NiaDispatchers {
+    IO
+}

core-common/src/main/java/com/google/samples/apps/nowinandroid/core/network/di/DispatchersModule.kt

@@ -14,26 +14,21 @@
  * limitations under the License.
  */
 
-package com.google.samples.apps.nowinandroid.core.network
+package com.google.samples.apps.nowinandroid.core.network.di
 
-import javax.inject.Inject
+import com.google.samples.apps.nowinandroid.core.network.Dispatcher
+import com.google.samples.apps.nowinandroid.core.network.NiaDispatchers.IO
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.InstallIn
+import dagger.hilt.components.SingletonComponent
 import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.MainCoroutineDispatcher
 
-interface NiaDispatchers {
+@Module
-    val IO: CoroutineDispatcher
+@InstallIn(SingletonComponent::class)
-
+object DispatchersModule {
-    val Default: CoroutineDispatcher
+    @Provides
-
+    @Dispatcher(IO)
-    val Main: MainCoroutineDispatcher
+    fun providesIODispatcher(): CoroutineDispatcher = Dispatchers.IO
-
-    val Unconfined: CoroutineDispatcher
-}
-
-class DefaultNiaDispatchers @Inject constructor() : NiaDispatchers {
-    override val IO: CoroutineDispatcher = Dispatchers.IO
-    override val Default: CoroutineDispatcher = Dispatchers.Default
-    override val Main: MainCoroutineDispatcher = Dispatchers.Main
-    override val Unconfined: CoroutineDispatcher = Dispatchers.Unconfined
 }

core-datastore/build.gradle

@@ -57,6 +57,8 @@ protobuf {
 }
 
 dependencies {
+    implementation project(':core-common')
+
     testImplementation project(':core-testing')
 
     implementation libs.kotlinx.coroutines.android

core-datastore/src/main/java/com/google/samples/apps/nowinandroid/core/datastore/di/DataStoreModule.kt

@@ -22,12 +22,17 @@ import androidx.datastore.core.DataStoreFactory
 import androidx.datastore.dataStoreFile
 import com.google.samples.apps.nowinandroid.core.datastore.UserPreferences
 import com.google.samples.apps.nowinandroid.core.datastore.UserPreferencesSerializer
+import com.google.samples.apps.nowinandroid.core.network.Dispatcher
+import com.google.samples.apps.nowinandroid.core.network.NiaDispatchers.IO
 import dagger.Module
 import dagger.Provides
 import dagger.hilt.InstallIn
 import dagger.hilt.android.qualifiers.ApplicationContext
 import dagger.hilt.components.SingletonComponent
 import javax.inject.Singleton
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.SupervisorJob
 
 @Module
 @InstallIn(SingletonComponent::class)
@@ -37,10 +42,12 @@ object DataStoreModule {
     @Singleton
     fun providesUserPreferencesDataStore(
         @ApplicationContext context: Context,
+        @Dispatcher(IO) ioDispatcher: CoroutineDispatcher,
         userPreferencesSerializer: UserPreferencesSerializer
     ): DataStore<UserPreferences> =
         DataStoreFactory.create(
-            serializer = userPreferencesSerializer
+            serializer = userPreferencesSerializer,
+            scope = CoroutineScope(ioDispatcher + SupervisorJob())
         ) {
             context.dataStoreFile("user_preferences.pb")
         }

core-domain/build.gradle

@@ -38,6 +38,7 @@ android {
 }
 
 dependencies {
+    implementation project(':core-common')
     implementation project(':core-model')
     implementation project(':core-database')
     implementation project(':core-datastore')

core-domain/src/main/java/com/google/samples/apps/nowinandroid/core/domain/repository/fake/FakeNewsRepository.kt

@@ -18,8 +18,10 @@ package com.google.samples.apps.nowinandroid.core.domain.repository.fake
 
 import com.google.samples.apps.nowinandroid.core.domain.repository.NewsRepository
 import com.google.samples.apps.nowinandroid.core.model.data.NewsResource
-import com.google.samples.apps.nowinandroid.core.network.NiaDispatchers
+import com.google.samples.apps.nowinandroid.core.network.Dispatcher
+import com.google.samples.apps.nowinandroid.core.network.NiaDispatchers.IO
 import javax.inject.Inject
+import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.flowOf
 import kotlinx.serialization.json.Json
@@ -31,7 +33,7 @@ import kotlinx.serialization.json.Json
  * backend.
  */
 class FakeNewsRepository @Inject constructor(
-    private val dispatchers: NiaDispatchers,
+    @Dispatcher(IO) private val ioDispatcher: CoroutineDispatcher,
     private val networkJson: Json
 ) : NewsRepository {
 

core-domain/src/main/java/com/google/samples/apps/nowinandroid/core/domain/repository/fake/FakeTopicsRepository.kt

@@ -19,10 +19,12 @@ package com.google.samples.apps.nowinandroid.core.domain.repository.fake
 import com.google.samples.apps.nowinandroid.core.datastore.NiaPreferences
 import com.google.samples.apps.nowinandroid.core.domain.repository.TopicsRepository
 import com.google.samples.apps.nowinandroid.core.model.data.Topic
-import com.google.samples.apps.nowinandroid.core.network.NiaDispatchers
+import com.google.samples.apps.nowinandroid.core.network.Dispatcher
+import com.google.samples.apps.nowinandroid.core.network.NiaDispatchers.IO
 import com.google.samples.apps.nowinandroid.core.network.fake.FakeDataSource
 import com.google.samples.apps.nowinandroid.core.network.model.NetworkTopic
 import javax.inject.Inject
+import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.flow
 import kotlinx.coroutines.flow.flowOn
@@ -37,7 +39,7 @@ import kotlinx.serialization.json.Json
  * backend.
  */
 class FakeTopicsRepository @Inject constructor(
-    private val dispatchers: NiaDispatchers,
+    @Dispatcher(IO) private val ioDispatcher: CoroutineDispatcher,
     private val networkJson: Json,
     private val niaPreferences: NiaPreferences
 ) : TopicsRepository {
@@ -52,7 +54,7 @@ class FakeTopicsRepository @Inject constructor(
             }
         )
     }
-        .flowOn(dispatchers.IO)
+        .flowOn(ioDispatcher)
 
     override suspend fun setFollowedTopicIds(followedTopicIds: Set<Int>) =
         niaPreferences.setFollowedTopicIds(followedTopicIds)

core-domain/src/test/java/com/google/samples/apps/nowinandroid/core/domain/repository/FakeNewsRepositoryTest.kt

@@ -17,7 +17,7 @@
 package com.google.samples.apps.nowinandroid.core.domain.repository
 
 import com.google.samples.apps.nowinandroid.core.domain.repository.fake.FakeNewsRepository
-import com.google.samples.apps.nowinandroid.core.network.DefaultNiaDispatchers
+import kotlinx.coroutines.test.StandardTestDispatcher
 import kotlinx.serialization.json.Json
 import org.junit.Before
 
@@ -25,11 +25,12 @@ class FakeNewsRepositoryTest {
 
     private lateinit var subject: FakeNewsRepository
 
+    private val testDispatcher = StandardTestDispatcher()
+
     @Before
     fun setup() {
         subject = FakeNewsRepository(
-            // TODO: Create test-specific NiaDispatchers
+            ioDispatcher = testDispatcher,
-            dispatchers = DefaultNiaDispatchers(),
             networkJson = Json { ignoreUnknownKeys = true }
         )
     }

core-network/build.gradle

@@ -38,6 +38,7 @@ android {
 }
 
 dependencies {
+    implementation project(':core-common')
     implementation project(':core-model')
 
     testImplementation project(':core-testing')

core-network/src/main/java/com/google/samples/apps/nowinandroid/core/network/di/NetworkModule.kt

@@ -16,9 +16,7 @@
 
 package com.google.samples.apps.nowinandroid.core.network.di
 
-import com.google.samples.apps.nowinandroid.core.network.DefaultNiaDispatchers
 import com.google.samples.apps.nowinandroid.core.network.NiANetwork
-import com.google.samples.apps.nowinandroid.core.network.NiaDispatchers
 import com.google.samples.apps.nowinandroid.core.network.fake.FakeNiANetwork
 import dagger.Binds
 import dagger.Module
@@ -37,9 +35,6 @@ interface NetworkModule {
         fakeNiANetwork: FakeNiANetwork
     ): NiANetwork
 
-    @Binds
-    fun bindsNiaDispatchers(defaultNiaDispatchers: DefaultNiaDispatchers): NiaDispatchers
-
     companion object {
         @Provides
         @Singleton

core-network/src/main/java/com/google/samples/apps/nowinandroid/core/network/fake/FakeNiANetwork.kt

@@ -16,11 +16,13 @@
 
 package com.google.samples.apps.nowinandroid.core.network.fake
 
+import com.google.samples.apps.nowinandroid.core.network.Dispatcher
 import com.google.samples.apps.nowinandroid.core.network.NiANetwork
-import com.google.samples.apps.nowinandroid.core.network.NiaDispatchers
+import com.google.samples.apps.nowinandroid.core.network.NiaDispatchers.IO
 import com.google.samples.apps.nowinandroid.core.network.model.NetworkNewsResource
 import com.google.samples.apps.nowinandroid.core.network.model.NetworkTopic
 import javax.inject.Inject
+import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.withContext
 import kotlinx.serialization.Serializable
 import kotlinx.serialization.decodeFromString
@@ -30,16 +32,16 @@ import kotlinx.serialization.json.Json
  * [NiANetwork] implementation that provides static news resources to aid development
  */
 class FakeNiANetwork @Inject constructor(
-    private val dispatchers: NiaDispatchers,
+    @Dispatcher(IO) private val ioDispatcher: CoroutineDispatcher,
     private val networkJson: Json
 ) : NiANetwork {
     override suspend fun getTopics(): List<NetworkTopic> =
-        withContext(dispatchers.IO) {
+        withContext(ioDispatcher) {
             networkJson.decodeFromString(FakeDataSource.topicsData)
         }
 
     override suspend fun getNewsResources(): List<NetworkNewsResource> =
-        withContext(dispatchers.IO) {
+        withContext(ioDispatcher) {
             networkJson.decodeFromString<ResourceData>(FakeDataSource.data).resources
         }
 }

core-network/src/test/java/com/google/samples/apps/nowinandroid/core/network/fake/FakeNiANetworkTest.kt

@@ -16,7 +16,7 @@
 
 package com.google.samples.apps.nowinandroid.core.network.fake
 
-import com.google.samples.apps.nowinandroid.core.network.DefaultNiaDispatchers
+import kotlinx.coroutines.test.StandardTestDispatcher
 import kotlinx.coroutines.test.runTest
 import kotlinx.serialization.json.Json
 import org.junit.Assert.assertEquals
@@ -27,17 +27,18 @@ class FakeNiANetworkTest {
 
     private lateinit var subject: FakeNiANetwork
 
+    private val testDispatcher = StandardTestDispatcher()
+
     @Before
     fun setUp() {
         subject = com.google.samples.apps.nowinandroid.core.network.fake.FakeNiANetwork(
-            // TODO: Create test-specific NiaDispatchers
+            ioDispatcher = testDispatcher,
-            dispatchers = DefaultNiaDispatchers(),
             networkJson = Json { ignoreUnknownKeys = true }
         )
     }
 
     @Test
-    fun testDeserializationOfTopics() = runTest {
+    fun testDeserializationOfTopics() = runTest(testDispatcher) {
         assertEquals(
             FakeDataSource.sampleTopic,
             subject.getTopics().first()
@@ -45,7 +46,7 @@ class FakeNiANetworkTest {
     }
 
     @Test
-    fun testDeserializationOfNewsResources() = runTest {
+    fun testDeserializationOfNewsResources() = runTest(testDispatcher) {
         assertEquals(
             FakeDataSource.sampleResource,
             subject.getNewsResources().first()

core-testing/build.gradle

@@ -16,6 +16,7 @@
 plugins {
     id 'com.android.library'
     id 'kotlin-android'
+    id 'kotlin-kapt'
 }
 
 android {
@@ -35,9 +36,13 @@ android {
 }
 
 dependencies {
+    implementation project(':core-common')
     implementation project(':core-domain')
     implementation project(':core-model')
 
+    implementation libs.hilt.android
+    kapt libs.hilt.compiler
+
     api libs.junit4
     api libs.mockk
     api libs.androidx.test.core

core-testing/src/main/java/com/google/samples/apps/nowinandroid/core/testing/di/TestDispatcherModule.kt

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.samples.apps.nowinandroid.core.testing.di
+
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.InstallIn
+import dagger.hilt.components.SingletonComponent
+import javax.inject.Singleton
+import kotlinx.coroutines.test.TestDispatcher
+import kotlinx.coroutines.test.UnconfinedTestDispatcher
+
+@Module
+@InstallIn(SingletonComponent::class)
+object TestDispatcherModule {
+    @Provides
+    @Singleton
+    fun providesTestDispatcher(): TestDispatcher = UnconfinedTestDispatcher()
+}

core-testing/src/main/java/com/google/samples/apps/nowinandroid/core/testing/di/TestDispatchersModule.kt

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.samples.apps.nowinandroid.core.testing.di
+
+import com.google.samples.apps.nowinandroid.core.network.Dispatcher
+import com.google.samples.apps.nowinandroid.core.network.NiaDispatchers.IO
+import com.google.samples.apps.nowinandroid.core.network.di.DispatchersModule
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.components.SingletonComponent
+import dagger.hilt.testing.TestInstallIn
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.test.TestDispatcher
+
+@Module
+@TestInstallIn(
+    components = [SingletonComponent::class],
+    replaces = [DispatchersModule::class],
+)
+object TestDispatchersModule {
+    @Provides
+    @Dispatcher(IO)
+    fun providesIODispatcher(testDispatcher: TestDispatcher): CoroutineDispatcher = testDispatcher
+}