测试导航组件："does not have a NavController"

Question

我正在实施Espresso测试。我正在使用一个具有NavGraph作用域ViewModel的Fragment。问题是，当我尝试测试Fragment时，我得到了IllegalStateException，因为Fragment没有设置NavController。如何解决此问题？

class MyFragment : Fragment(), Injectable {
private val viewModel by navGraphViewModels<MyViewModel>(R.id.scoped_graph){
viewModelFactory
}
@Inject
lateinit var viewModelFactory: ViewModelProvider.Factory
//Other stuff
}

测试等级：

class FragmentTest {
class TestMyFragment: MyFragment(){
val navMock = mock<NavController>()
override fun getNavController(): NavController {
return navMock
}
}
@Mock
private lateinit var viewModel: MyViewModel
private lateinit var scenario: FragmentScenario<TestMyFragment>
@Before
fun prepareTest(){
MockitoAnnotations.initMocks(this)
scenario = launchFragmentInContainer<TestMyFragment>(themeResId = R.style.Theme_AppCompat){
TestMyFragment().apply {
viewModelFactory = ViewModelUtil.createFor(viewModel)
}
}
// My test
}

我得到的例外：

java.lang.IllegalStateException: View android.widget.ScrollView does not have a NavController setjava.lang.IllegalStateException

Answer 1

如文档中所示，以下是建议的方法：

// Create a mock NavController
val mockNavController = mock(NavController::class.java)
scenario = launchFragmentInContainer<TestMyFragment>(themeResId = R.style.Theme_AppCompat) {
TestMyFragment().also { fragment ->     
// In addition to returning a new instance of our Fragment,
// get a callback whenever the fragment’s view is created
// or destroyed so that we can set the mock NavController
fragment.viewLifecycleOwnerLiveData.observeForever { viewLifecycleOwner ->
if (viewLifecycleOwner != null) {
// The fragment’s view has just been created
Navigation.setViewNavController(fragment.requireView(), mockNavController)
}
}
}
}

之后，您可以对模拟mockNavController进行验证，如下所示：

verify(mockNavController).navigate(SearchFragmentDirections.showRepo("foo", "bar"))

请参阅架构组件示例以供参考。

---

文档中也提到了另一种方法：

// Create a graphical FragmentScenario for the TitleScreen
val titleScenario = launchFragmentInContainer<TitleScreen>()
// Set the NavController property on the fragment
titleScenario.onFragment { fragment ->
Navigation.setViewNavController(fragment.requireView(), mockNavController)
}

如果在onViewCreated()(包括(之前与NavController发生交互，则此方法将不起作用。使用这种方法onFragment()会在生命周期中设置mockNavController太晚，导致findNavController()调用失败。作为一种适用于所有情况的统一方法，我建议使用第一种方法。

Answer 2

您缺少设置NavController:

testFragmentScenario.onFragment {
Navigation.setViewNavController(it.requireView(), mockNavController)
}