Navigation components - Mocking Navcontroller graph

Issue

I'm using navigation components and I'm trying to test my Fragment with instrumented test. The fragment has a custom toolbar initialized in onViewCreated method by an extension function.

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    tbBlack.init()
}


fun androidx.appcompat.widget.Toolbar.init(
    menuId: Int? = null
) {
    title = ""
    menuId?.let {
        inflateMenu(it)
    }

    findNavController().let {
        it.graph.let { graph ->
            val configuration = AppBarConfiguration(graph)
            setupWithNavController(it, configuration)
        }
    }
}

During the initialization of the scenario in my instrumented test, the test crashes due to a null graph on the Nav Controller.

The nav controller is mocked in the test, as well as the graph like below:

@RunWith(AndroidJUnit4::class)
class LoginFragmentTest {
    @Test
    fun testEmptyFields() {
        val mockNavController = mock(NavController::class.java)
        val mockGraph = mock(NavGraph::class.java)
        mockNavController.graph = mockGraph

        val scenario = launchFragmentInContainer(themeResId = R.style.AppTheme) {
            LoginFragment().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)
                    }
                }

            }
        }

        scenario.onFragment {
            it.run {
                val viewsIds =
                    listOf(R.id.etEmailAddress, R.id.etPassword)

                for (viewId in viewsIds) {
                    onView(ViewMatchers.withId(viewId))
                        .perform(ViewActions.replaceText(""))
                    Thread.sleep(500)
                    onView(ViewMatchers.withId(R.id.btLogin)).check(
                        ViewAssertions.matches(
                            CoreMatchers.not(
                                ViewMatchers.isEnabled()
                            )
                        )
                    )
                }
            }
        }
    }
}

Am I missing something in the mocking of the navController?

Solution

I solved by using the new TestNavHostController provided by androidx navigation test library

Basically, do:

1. Import the dependency in your (app) gradle:

dependencies {
  def nav_version = "2.3.0-alpha06"

  androidTestImplementation "androidx.navigation:navigation-testing:$nav_version"
}

2. Mock your nav controller by using TestNavHostController in your androidTest:

 // Create a TestNavHostController
val navController = TestNavHostController(
            ApplicationProvider.getApplicationContext())

val fragmentArgs = Bundle().apply {
            putParcelable(Constants.RETAIL_CLICK_SOURCE_ID, RetailDetailsClicked.Source.LIST)
            putParcelable(Constants.RETAIL_ID, retail)
        }
        navController.setGraph(R.navigation.retail_details_graph)

        launchFragmentInContainer(
            fragmentArgs, R.style.AppTheme
        ) {
            RetailDetailsFragment().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(), navController)
                    }
                }
            }
        }

That's it!

Answered By - Nicola Gallazzi