test: add Unit tests PixabayImagePagingSourceTest.

core/data/build.gradle.kts

@@ -1,6 +1,7 @@
 plugins {
     alias(libs.plugins.pq.android.library)
     alias(libs.plugins.pq.android.hilt)
+    id("kotlinx-serialization")
 }
 
 android {
@@ -18,4 +19,6 @@ dependencies {
     implementation(project(":core:network"))
     implementation(project(":core:model"))
     implementation(project(":core:datastore"))
+
+    implementation(libs.kotlinx.serialization.json)
 }

core/data/src/main/java/com/wei/picquest/core/data/repository/DefaultSearchImagesRepository.kt

@@ -6,8 +6,8 @@ import androidx.paging.PagingData
 import androidx.paging.map
 import com.wei.picquest.core.data.model.ImageDetail
 import com.wei.picquest.core.data.model.asExternalModel
-import com.wei.picquest.core.data.pagingsource.PixabayImagePagingSource
 import com.wei.picquest.core.network.PqNetworkDataSource
+import com.wei.picquest.core.network.pagingsource.PixabayImagePagingSource
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.map
 import javax.inject.Inject

core/data/src/main/java/com/wei/picquest/core/data/repository/DefaultSearchVideosRepository.kt

@@ -6,8 +6,8 @@ import androidx.paging.PagingData
 import androidx.paging.map
 import com.wei.picquest.core.data.model.VideoDetail
 import com.wei.picquest.core.data.model.asExternalModel
-import com.wei.picquest.core.data.pagingsource.PixabayVideoPagingSource
 import com.wei.picquest.core.network.PqNetworkDataSource
+import com.wei.picquest.core.network.pagingsource.PixabayVideoPagingSource
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.map
 import javax.inject.Inject

core/network/build.gradle.kts

@@ -24,6 +24,8 @@ secrets {
 }
 
 dependencies {
+    implementation(project(":core:common"))
+
     // Okhttp Interceptor
     implementation(libs.okhttp.logging)
 

core/network/src/main/assets/images_page_end.json

@@ -0,0 +1,5 @@
+{
+  "total": 7,
+  "totalHits": 7,
+  "hits": []
+}

core/network/src/main/assets/videos_page_end.json

@@ -0,0 +1,5 @@
+{
+  "total": 7,
+  "totalHits": 7,
+  "hits": []
+}

core/network/src/main/java/JvmUnitTestFakeAssetManager.kt

@@ -0,0 +1,26 @@
+import androidx.annotation.VisibleForTesting
+import com.wei.picquest.core.network.fake.FakeAssetManager
+import java.io.File
+import java.io.InputStream
+import java.util.Properties
+
+/**
+ * This class helps with loading Android `/assets` files, especially when running JVM unit tests.
+ * It must remain on the root package for an easier [Class.getResource] with relative paths.
+ * @see <a href="https://developer.android.com/reference/tools/gradle-api/7.3/com/android/build/api/dsl/UnitTestOptions">UnitTestOptions</a>
+ */
+@VisibleForTesting
+internal object JvmUnitTestFakeAssetManager : FakeAssetManager {
+    private val config =
+        requireNotNull(javaClass.getResource("com/android/tools/test_config.properties")) {
+            """
+            Missing Android resources properties file.
+            Did you forget to enable the feature in the gradle build file?
+            android.testOptions.unitTests.isIncludeAndroidResources = true
+            """.trimIndent()
+        }
+    private val properties = Properties().apply { config.openStream().use(::load) }
+    private val assets = File(properties["android_merged_assets"].toString())
+
+    override fun open(fileName: String): InputStream = File(assets, fileName).inputStream()
+}

core/network/src/main/java/com/wei/picquest/core/network/fake/FakeAssetManager.kt

@@ -0,0 +1,7 @@
+package com.wei.picquest.core.network.fake
+
+import java.io.InputStream
+
+fun interface FakeAssetManager {
+    fun open(fileName: String): InputStream
+}

core/network/src/main/java/com/wei/picquest/core/network/fake/FakePqNetworkDataSource.kt

@@ -0,0 +1,56 @@
+package com.wei.picquest.core.network.fake
+
+import JvmUnitTestFakeAssetManager
+import com.wei.picquest.core.network.Dispatcher
+import com.wei.picquest.core.network.PqDispatchers
+import com.wei.picquest.core.network.PqNetworkDataSource
+import com.wei.picquest.core.network.model.NetworkSearchImages
+import com.wei.picquest.core.network.model.NetworkSearchVideos
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.withContext
+import kotlinx.serialization.ExperimentalSerializationApi
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.decodeFromStream
+import org.jetbrains.annotations.VisibleForTesting
+
+class FakePqNetworkDataSource(
+    @Dispatcher(PqDispatchers.IO) private val ioDispatcher: CoroutineDispatcher,
+    private val networkJson: Json,
+    private val assets: FakeAssetManager = JvmUnitTestFakeAssetManager,
+) : PqNetworkDataSource {
+
+    private var shouldReturnErrorForImages = false
+
+    @VisibleForTesting
+    fun setReturnErrorForImages(shouldReturnError: Boolean) {
+        shouldReturnErrorForImages = shouldReturnError
+    }
+
+    @OptIn(ExperimentalSerializationApi::class)
+    override suspend fun searchImages(query: String, page: Int, perPage: Int): NetworkSearchImages =
+        withContext(ioDispatcher) {
+            if (shouldReturnErrorForImages) {
+                throw Exception("Fake exception for images")
+            }
+            when (page) {
+                0 -> assets.open(IMAGES_PAGE1_ASSET).use(networkJson::decodeFromStream)
+                1 -> assets.open(IMAGES_PAGE2_ASSET).use(networkJson::decodeFromStream)
+                else -> {
+                    assets.open(IMAGES_PAGE_END_ASSET).use(networkJson::decodeFromStream)
+                }
+            }
+        }
+
+    @OptIn(ExperimentalSerializationApi::class)
+    override suspend fun searchVideos(query: String, page: Int, perPage: Int): NetworkSearchVideos =
+        withContext(ioDispatcher) {
+            assets.open(VIDEOS_PAGE_END_ASSET).use(networkJson::decodeFromStream)
+        }
+
+    companion object {
+        private const val IMAGES_PAGE1_ASSET = "images_page1.json"
+        private const val IMAGES_PAGE2_ASSET = "images_page2.json"
+        private const val IMAGES_PAGE_END_ASSET = "images_page_end.json"
+        private const val VIDEOS_PAGE_END_ASSET = "videos_page_end.json"
+    }
+}

core/data/src/main/java/com/wei/picquest/core/data/pagingsource/PixabayImagePagingSource.kt → core/network/src/main/java/com/wei/picquest/core/network/pagingsource/PixabayImagePagingSource.kt

@@ -1,4 +1,4 @@
-package com.wei.picquest.core.data.pagingsource
+package com.wei.picquest.core.network.pagingsource
 
 import androidx.paging.PagingSource
 import androidx.paging.PagingState

core/data/src/main/java/com/wei/picquest/core/data/pagingsource/PixabayVideoPagingSource.kt → core/network/src/main/java/com/wei/picquest/core/network/pagingsource/PixabayVideoPagingSource.kt

@@ -1,4 +1,4 @@
-package com.wei.picquest.core.data.pagingsource
+package com.wei.picquest.core.network.pagingsource
 
 import androidx.paging.PagingSource
 import androidx.paging.PagingState

core/network/src/test/java/com/wei/picquest/core/network/pagingsource/PixabayImagePagingSourceTest.kt

@@ -0,0 +1,101 @@
+package com.wei.picquest.core.network.pagingsource
+
+import JvmUnitTestFakeAssetManager
+import androidx.paging.PagingSource
+import com.google.common.truth.Truth.assertThat
+import com.wei.picquest.core.network.fake.FakePqNetworkDataSource
+import kotlinx.coroutines.test.StandardTestDispatcher
+import kotlinx.coroutines.test.runTest
+import kotlinx.serialization.json.Json
+import org.junit.Before
+import org.junit.Test
+
+/**
+ * Unit tests for [PixabayImagePagingSource].
+ *
+ * 遵循此模型，安排、操作、斷言：
+ * {Arrange}{Act}{Assert}
+ */
+class PixabayImagePagingSourceTest {
+
+    private lateinit var fakePqNetworkDataSource: FakePqNetworkDataSource
+    private lateinit var pixabayImagePagingSource: PixabayImagePagingSource
+
+    private val testDispatcher = StandardTestDispatcher()
+
+    @Before
+    fun setUp() {
+        fakePqNetworkDataSource = FakePqNetworkDataSource(
+            ioDispatcher = testDispatcher,
+            networkJson = Json { ignoreUnknownKeys = true },
+            assets = JvmUnitTestFakeAssetManager,
+        )
+        pixabayImagePagingSource = PixabayImagePagingSource(fakePqNetworkDataSource, "testQuery")
+    }
+
+    @Test
+    fun `load should return non-empty page for first and second page`() = runTest(testDispatcher) {
+        // Arrange
+        val firstPageKey = 0
+        val secondPageKey = 1
+
+        // Act
+        val firstPageResult = pixabayImagePagingSource.load(
+            PagingSource.LoadParams.Refresh(
+                key = firstPageKey,
+                loadSize = 20,
+                placeholdersEnabled = false,
+            ),
+        )
+        val secondPageResult = pixabayImagePagingSource.load(
+            PagingSource.LoadParams.Refresh(
+                key = secondPageKey,
+                loadSize = 20,
+                placeholdersEnabled = false,
+            ),
+        )
+
+        // Assert
+        assertThat(firstPageResult).isInstanceOf(PagingSource.LoadResult.Page::class.java)
+        assertThat((firstPageResult as PagingSource.LoadResult.Page).data).isNotEmpty()
+        assertThat(secondPageResult).isInstanceOf(PagingSource.LoadResult.Page::class.java)
+        assertThat((secondPageResult as PagingSource.LoadResult.Page).data).isNotEmpty()
+    }
+
+    @Test
+    fun `load should return empty page at end of pagination`() = runTest(testDispatcher) {
+        // Arrange
+        val endPageKey = 2 // Assuming this is the end
+
+        // Act
+        val endPageResult = pixabayImagePagingSource.load(
+            PagingSource.LoadParams.Refresh(
+                key = endPageKey,
+                loadSize = 20,
+                placeholdersEnabled = false,
+            ),
+        )
+
+        // Assert
+        assertThat(endPageResult).isInstanceOf(PagingSource.LoadResult.Page::class.java)
+        assertThat((endPageResult as PagingSource.LoadResult.Page).data).isEmpty()
+    }
+
+    @Test
+    fun `load should return error when data source throws exception`() = runTest {
+        // Arrange
+        fakePqNetworkDataSource.setReturnErrorForImages(true)
+
+        // Act
+        val result = pixabayImagePagingSource.load(
+            PagingSource.LoadParams.Refresh(
+                key = 0,
+                loadSize = 20,
+                placeholdersEnabled = false,
+            ),
+        )
+
+        // Assert
+        assertThat(result).isInstanceOf(PagingSource.LoadResult.Error::class.java)
+    }
+}