Testing classes using android.view.Menu

How to test with Menu in a unit test? One can definitely use mocking:

val mockMenuItem = mock<MenuItem>()

val myMockedMenu = mock<Menu> {
    when {findItem(any())} doReturn mockMenuItem
}

But you still get NullPointerException here and there, for example when testing BottomNavigationView that has its internal implementation of Menu and MenuItem. Urgh.

Maybe RoboMenu from Robolectric ? Makes creating fake easier, for example:

class FakeMenu(val menuItem: MenuItem): RoboMenu() {
    val idLookedUp = mutableListOf<Int>()
    override fun findItem(id: Int): MenuItem? {
        idLookedUp.add(id) // keep the Ids so we can compare later
        return menuItem
    }
}

With this we can then use something like assertThat() from Truth

    val myFakeMenu = FakeMenu(fakeMenuItem)
    ... // some test conditions
    assertThat(myFakeMenu.idLookedUp).isExactly(listOf(R.menu.menu_item1, R.menu.menu_item9))

versus Mockito’s verify() syntax.

    // how do I check which IDs were looked up without using a Capture?
    verify(mockMenu, times(2)).findItem(any())

However, is this a valid use of RoboMenu? Don’t know. If you know the definite answer, please let me know!