How do I unit test RecyclerView , LinearLayoutManager in Robolectric?

Question

How do I unit test RecyclerView, ScrollListener , LinearLayoutManager in Robolectric?

Im fairly new to this kind of testing but I really wanted to imitate gestures, especially scrolling.

Answer 1

I guess what you really wan't to test is your code and if it behaves as desired using these components.

Since the scope of your question is pretty wide, let me give it a use-case.:

Let's assume you have a fragment with a RecyclerView, which has a LinearLayoutManager. You want to test if a click on one of the items triggers the right method call on another layer. (Let's say you use MVP and that is the presenter)

A possible test could look like this.:

@RunWith(RobolectricGradleTestRunner::class)
@Config(constants = BuildConfig::class, sdk = intArrayOf(21))
class MyFragmentTest {

lateinit var fragment: MyFragment
lateinit var activityController: ActivityController<FragmentActivity>

@Before
@Throws(Exception::class)
fun setUp() {
    fragment = MyFragment()

    activityController = Robolectric.buildActivity(FragmentActivity::class.java)

    activityController.create().start().resume()

    activityController.get()
            .supportFragmentManager
            .beginTransaction()
            .add(fragment, null)
            .commit()
}

@Test
@Throws(Exception::class)
fun testClickEntry() {
    val recycler = fragment.view!!.findViewById(R.id.sideNavigationRecycler) as RecyclerView
    // workaround robolectric recyclerView issue
    recycler.measure(0,0)
    recycler.layout(0,0,100,1000)

    // lets just imply a certain item at position 0 for simplicity
    recycler.findViewHolderForAdapterPosition(0).itemView.performClick()

    // presenter is injected in my case, how this verification happens depends on how you manage your dependencies. 
    verify(fragment.presenter).onEntryClicked(MyNavigationEntry.XYZ)
}
}

Sorry for the syntax first of all, I use Kotlin in my tests.

I have to say though I'm not 100% happy with this by myself but i think its reasonable if you wan't to test the correct communication of your layers.