Integer gives NPE in launchFragmentInContainer bundle in espresso testing

You have not provided your launchFragmentInContainer implementation but I will answer based on my current setup and experience with fragments. This is the implementation I have (note we are using Hilt but it should be similar).

inline fun <reified T : Fragment> launchFragmentInHiltContainer(
        fragmentArgs: Bundle? = null,
        themeResId: Int = R.style.AppTheme,
        fragmentFactory: FragmentFactory? = null,
        crossinline action: T.() -> Unit = {}
    ) {
        val mainActivityIntent = Intent.makeMainActivity(
            ComponentName(
                ApplicationProvider.getApplicationContext(),
                HiltTestActivity::class.java
            )
        ).putExtra(
            "androidx.fragment.app.testing.FragmentScenario.EmptyFragmentActivity.THEME_EXTRAS_BUNDLE_KEY",
            themeResId
        )

        ActivityScenario.launch<HiltTestActivity>(mainActivityIntent).onActivity { activity ->
            fragmentFactory?.let {
                activity.supportFragmentManager.fragmentFactory = it
            }
            val fragment = activity.supportFragmentManager.fragmentFactory.instantiate(
                Preconditions.checkNotNull(T::class.java.classLoader),
                T::class.java.name
            )
            fragment.arguments = fragmentArgs

            activity.supportFragmentManager.beginTransaction()
                .add(android.R.id.content, fragment, "")
                .commitNow()

            (fragment as T).action()
        }

    }

Let's say you want to start a specific fragment named MyView, for this(and each fragment) you should have MyViewArgs(or similar) object. Then you can start it in this way:

val args = MyViewArgs(11111).toBundle()     
HiltFragmentUtil.launchFragmentInHiltContainer<MyView>(args)

This way you are providing the args the exact way the fragment expects them so if the arg is an int, then MyViewArgs will require it as int