Possible to mock/test Android ViewBinding interactions?

Question

currently trying to test the interactions with ViewBinding classes in Unit Tests

"Invalid Input" should {
    "disable the LoginButton" {
        val viewBinding: FrLoginBinding = mockk()

        InvalidInputViewStateBinder.bind(InvalidInput, viewBinding)

        verify { viewBinding.loginButton.isEnabled = false }
    }
}

something like this is what i had in mind. The Views in the ViewBinding are public final Properties and cannot easily be mocked. At least i'm unable to. Passing a View mock to create the ViewBinding also doesn't work, as i'd have to mock findViewById for it.

Has anyone tried this out and got it to work?

@mochadwi, I added an implementation details for how you would need to mock parts of the mocked viewbinding below. But you will need to the accesses of the mockked viewbinding before you can verify it. — Glo, Mar 04 '21 at 06:25

score 4 · Answer 1 · answered Jun 23 '20 at 19:15

I came across this same issue. Here is how I resolved it


@RunWith(PowerMockRunner::class)
@PrepareForTest(MyLayoutBinding::class)
class MyTestClass {

    @Mock
    lateinit var mMockViewBinding: MyLayoutBinding

    @Mock
    lateinit var mMockView: View

    @Mock
    lateinit var mMockTitleTv: TextView

    @Mock
    lateinit var mMockRootView: ConstraintLayout

    @Before
    fun setup() {
        MockitoAnnotations.initMocks(this)
        PowerMockito.mockStatic(MyLayoutBinding::class.java)
        whenever(MyLayoutBinding.bind(mMockView)).thenReturn(mMockViewBinding)
        
        // Use Whitebox for each view component in the layout.
        Whitebox.setInternalState(mMockBinding, "title", mMockTitleTv)
        
        // Because 'getRoot' is part of the ViewBinding interface, we just mock the method.
        whenever(mMockBinding.root).thenReturn(mMockRootView)
    }


}

Use Whitebox to set the properties (i.e. the views by id) and mock the getRoot() interface method to set the root to your mocked root view.

so for each view of the LayoutBinding i need to provide a mock and set the internal state with Whitebox? Even if have no assertions on them? — Flo We, Mar 05 '21 at 10:24
@FloWe You should be able to just mock the specific view and set it with whitebox. — Glo, May 12 '21 at 18:58
Do you mean `mMockBinding.root` or `mMockViewBinding.root` as per your provided snippet? — Ankush, Nov 25 '22 at 01:39

Possible to mock/test Android ViewBinding interactions?

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