Backstack with espresso about simple-stack HOT 3 CLOSED

Thank you very much for this answer. It was indeed spot on.

To give the exact code to achieve that, because I just tried it and it's working wonderfully.

You need the Activity Rule :
@Rule @JvmField val activityRule = ActivityScenarioRule(MainActivity::class.java)
And the test to access to the Fragment :

`@Test
fun testFragmentIsVisible() {

    activityRule.run {
        scenario.onActivity {
                activity -> Navigator.getBackstack(activity).setHistory(History.of(YourFragmentKey()), StateChange.REPLACE)
        }
    }

    // your action to modify the view or whatever you wanna do.
}`

You said, "when I was using espresso", does it mean that you use something else now?

Thank you for your help!

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@MikaReesu this is an interesting question, because based on the FragmentScenario source code, the problem is that when you use launchFragmentInContainer<T: Fragment>, it internally uses an EmptyFragmentActivity rather than your MainActivity.

https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:fragment/fragment-testing-manifest/src/main/java/androidx/fragment/app/testing/EmptyFragmentActivity.kt;l=30

The EmptyFragmentActivity has support for a custom theme, but no other means of customization.

Based on FragmentScenario source code, this cannot be customized when using FragmentScenario.

https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:fragment/fragment-testing/src/main/java/androidx/fragment/app/testing/FragmentScenario.kt;l=515?q=launchFragmentInContainer

So even though you have Navigator.install() and a BackstackHost installed in MainActivity, it appears that the Activity in EmptyFragmentActivity has no idea how to do that. There seems to also be no way to access this class from the outside and make any necessary customizations. Makes me wonder what FragmentScenario is even doing, then.

Personally, when I was using Espresso, I was using getInstrumentation().runOnMainSync() directly instead of androidx.test.

However, it appears that ActivityScenario.onActivity does exactly that: https://github.com/android/android-test/blob/5d69602b7f5950e8c62027e7eeb7f613e5f3b015/core/java/androidx/test/core/app/ActivityScenario.java#L802

Which means that instead of using launchFragmentInContainer, you can theoretically use activityScenario.onActivity { activity -> Navigator.getBackstack(activity).setHistory(History.of(YourFragmentKey()), StateChange.REPLACE) } in order to get the fragment showing, and you don't need launchFragmentInContainer as that starts using EmptyFragmentActivity instead of your MainActivity.

Hope that helps.

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You said, "when I was using espresso", does it mean that you use something else now?

Mistake in wording tbh. Espresso is still the best way to automate UI tests when using Views.

Thank you for your help!

Glad it works 😄

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