Android 33中如何Mock ContentResolver？MediaStore测试查询为空

问题根源 #

你直接操作真实MediaStore的方式在测试环境中行不通：

• 单元测试里没有真实的系统ContentProvider，插入操作根本没写入数据
• Instrumented测试中，MediaStore受系统权限和沙箱限制，手动插入的内容不会被真实Provider识别

官方推荐的两种可行方案如下：

方案一：自定义Fake ContentProvider #

创建一个内存版的Fake MediaStore Provider，完全控制数据的插入和查询：

1. 实现FakeMediaStoreProvider #

class FakeMediaStoreProvider : ContentProvider() {
    private val db = SQLiteDatabase.create(null).apply {
        execSQL("""
            CREATE TABLE audio (
                ${MediaStore.Audio.Media._ID} INTEGER PRIMARY KEY,
                ${MediaStore.Audio.Media.DISPLAY_NAME} TEXT,
                ${MediaStore.Audio.Media.IS_MUSIC} INTEGER
            )
        """.trimIndent())
    }

    override fun onCreate(): Boolean = true

    override fun insert(uri: Uri, values: ContentValues?): Uri? {
        val id = db.insert("audio", null, values)
        return Uri.parse("content://fake.media/audio/$id")
    }

    override fun query(
        uri: Uri,
        projection: Array<String>?,
        selection: String?,
        selectionArgs: Array<String>?,
        sortOrder: String?
    ): Cursor? {
        return db.query(
            "audio",
            projection,
            selection,
            selectionArgs,
            null,
            null,
            sortOrder
        )
    }

    // 其他未用到的方法返回默认值即可
    override fun update(uri: Uri, values: ContentValues?, selection: String?, selectionArgs: Array<String>?): Int = 0
    override fun delete(uri: Uri, selection: String?, selectionArgs: Array<String>?): Int = 0
    override fun getType(uri: Uri): String? = "vnd.android.cursor.dir/audio"
}

2. 在测试中注册并使用 #

@RunWith(AndroidJUnit4::class)
class MusicStoreTest {
    private lateinit var fakeResolver: ContentResolver

    @Before
    fun setup() {
        // 注册Fake Provider
        val context = ApplicationProvider.getApplicationContext<Context>()
        val authority = "fake.media"
        context.contentResolver.registerContentProvider(
            authority,
            FakeMediaStoreProvider::class.java.name,
            null
        )
        fakeResolver = context.contentResolver
    }

    @Test
    fun getMusicFromMediaStore_returnsExpectedList() {
        // 插入测试数据
        val values = ContentValues().apply {
            put(MediaStore.Audio.Media._ID, 1L)
            put(MediaStore.Audio.Media.DISPLAY_NAME, "test.mp3")
            put(MediaStore.Audio.Media.IS_MUSIC, 1)
        }
        fakeResolver.insert(Uri.parse("content://fake.media/audio"), values)

        // 调用待测试方法
        val result = getMusicFromMediaStore(fakeResolver)

        // 断言结果
        assertEquals(1, result.size)
        assertEquals("test.mp3", result[0].displayName)
    }
}

方案二：用Mockito Mock ContentResolver #

如果不需要测试真实Provider的逻辑，直接Mock查询结果更高效：

1. 构造Mock Cursor #

private fun createMockCursor(): Cursor {
    val cursor = mock(Cursor::class.java)
    // 模拟Cursor包含一行数据
    `when`(cursor.count).thenReturn(1)
    `when`(cursor.moveToFirst()).thenReturn(true)
    
    // 模拟列索引
    val idIndex = 0
    val nameIndex = 1
    val isMusicIndex = 2
    `when`(cursor.getColumnIndex(MediaStore.Audio.Media._ID)).thenReturn(idIndex)
    `when`(cursor.getColumnIndex(MediaStore.Audio.Media.DISPLAY_NAME)).thenReturn(nameIndex)
    `when`(cursor.getColumnIndex(MediaStore.Audio.Media.IS_MUSIC)).thenReturn(isMusicIndex)
    
    // 模拟数据返回
    `when`(cursor.getLong(idIndex)).thenReturn(1L)
    `when`(cursor.getString(nameIndex)).thenReturn("test.mp3")
    `when`(cursor.getInt(isMusicIndex)).thenReturn(1)
    
    // 模拟关闭操作
    `when`(cursor.close()).thenReturn(Unit)
    return cursor
}

2. 编写测试用例 #

@Test
fun getMusicFromMediaStore_returnsExpectedList() {
    val mockResolver = mock(ContentResolver::class.java)
    val mockCursor = createMockCursor()
    
    // 配置Mock：当调用query时返回构造好的Cursor
    `when`(mockResolver.query(
        eq(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI),
        any(),
        any(),
        any(),
        any()
    )).thenReturn(mockCursor)
    
    // 调用待测试方法
    val result = getMusicFromMediaStore(mockResolver)
    
    // 断言结果
    assertEquals(1, result.size)
    assertEquals("test.mp3", result[0].displayName)
    
    // 验证Cursor被关闭
    verify(mockCursor).close()
}

注意事项 #

• 单元测试优先用Mock方案，速度快且无需依赖Android环境
• 如果需要测试Provider的查询逻辑（比如筛选、排序），用Fake Provider更贴近真实场景
• 避免在测试中操作真实MediaStore，系统限制会导致测试不稳定

内容的提问来源于stack exchange，提问作者John Glen