Android Firebase Junit4 模拟数据库。如何模拟数据库children？

Question

需要一些帮助来测试我的应用程序。 我想验证视图模型的乐趣 writeNewTask()。它必须将 Task object 添加到名为 tasks 和个人 id[ 的 parents 下的数据库中=27=] 每个任务。

fun writeNewTask(name: String?, orphanage: String?) {
        val id = database.push().key!!
        val task = Task(id, name, orphanage)
        database.child("tasks").child(id).setValue(task)
    }

我正在使用 PowerMock。所以，这就是我的测试结果

@RunWith(PowerMockRunner::class)
@PowerMockRunnerDelegate(JUnit4::class)
@PrepareForTest(FirebaseDatabase::class, AddTaskViewModel::class, DatabaseReference::class)
@PowerMockIgnore("org.mockito.*", "org.robolectric.*", "android.*", "androidx.*")
class AddTaskViewModelTest {

    @Mock
    lateinit var mockedDatabase: FirebaseDatabase
    @Mock
    lateinit var databaseReference: DatabaseReference
    @Mock
    lateinit var viewModel: AddTaskViewModel

    @Before
    fun before() {
        viewModel = PowerMockito.mock(AddTaskViewModel::class.java)
        databaseReference = PowerMockito.mock(DatabaseReference::class.java)

        PowerMockito.mockStatic(AddTaskViewModel::class.java)
        PowerMockito.mockStatic(DatabaseReference::class.java)

        PowerMockito.mockStatic(FirebaseDatabase::class.java)
        `when`(FirebaseDatabase.getInstance()).thenReturn(mockedDatabase)

        mockedDatabase = PowerMockito.mock(FirebaseDatabase::class.java)
        `when`(mockedDatabase.reference).thenReturn(databaseReference)
    }

    @Test
    fun writeNewTaskTest() {
        val id = "1"
        `when`(databaseReference.key).thenReturn(id)
        val name = "name"
        val orphanage = "orphanage"
        val task = Task(id, name, orphanage)

        viewModel.writeNewTask(name, orphanage)

        verify(databaseReference)
            .child("tasks")
            .child(id)
            .setValue(task)
    }
}

我发现了这个错误。调试后我发现 child("tasks") 是 null

databaseReference.child("tasks");
-> at com.example.application.viewModel.AddTaskViewModelTest.writeNewTaskTest(AddTaskViewModelTest.kt:59)
Actually, there were zero interactions with this mock.

Wanted but not invoked:
databaseReference.child("tasks");
-> at com.example.application.viewModel.AddTaskViewModelTest.writeNewTaskTest(AddTaskViewModelTest.kt:59)
Actually, there were zero interactions with this mock.

Answer 1

发生这种情况是因为您对数据库的引用与您在 ViewModel 中的引用不同。所以让我们假设你有一个 ViewModel，它在它的构造函数中获取一个数据库：

class AddTaskViewModel(private val database: FirebaseDatabase): ViewModel()

因此，要测试您的 ViewModel，您需要创建它的实例，而不是模拟它。在您的代码中应该如下所示：

@Before
fun before() {
    databaseReference = mock(DatabaseReference::class.java)
    mockedDatabase = mock(FirebaseDatabase::class.java)
    `when`(mockedDatabase.reference).thenReturn(databaseReference)

    viewModel = AddTaskViewModel(mockedDatabase)
}

另外你不需要PowerMockito来测试这个，Mockito本身就足够了