Android - Testing navigation with NavigationComponent

I’m having trouble testing my navigation with NavigationComponent, Espresso and Mockito. I have this simple test:

@Test
fun testNavigation(){

    val mockNavController = mock(NavController::class.java)

    val firstScenario = launchFragmentInContainer<FirstFragment>()

    firstScenario.onFragment { fragment ->
        Navigation.setViewNavController(fragment.requireView(), mockNavController)
    }

    val expectedBundle = bundleOf(ARG_A to true)

    onView(withId(R.id.button)).perform(click())

    verify(mockNavController).navigate(R.id.action_first_fragment_to_second_fragment, expectedBundle)
}

The test fails with this error:

Argument(s) are different! Wanted:
navController.navigate(
2131361850,
Bundle[{ARG_A=true}]
);
-> at FirstFragmentTest.testNavigation(FirstFragmentTest.kt:60)

Actual invocation has different arguments:
navController.navigate(
2131361850,
Bundle[{ARG_A=true}]
);
-> at FirstFragment$onViewCreated$2.onClick(FirstFragment.kt:67)

The arguments and id are exactly the same, the only difference is that last line in the error showing where the on click was invoked. Also, the onClick() method in my test doesn’t even seem to open the second fragment. It just stays on the first fragment.

Does someone know what’s going wrong?
Thanks in advance!