Launching Fragments with FragmentScenario — Test Fragments in Isolation

FragmentScenario hosts a single fragment inside an internal EmptyFragmentActivity so the fragment's onCreate / onViewCreated / lifecycle can be exercised without a real screen. Two entry points exist: launchFragmentInContainer<F>() adds the fragment to android.R.id.content (full lifecycle including view), and launchFragment<F>() attaches it with no container (headless). The default theme extends android:Theme.WithActionBar, NOT AppCompat — overriding via themeResId is required for any AppCompat widget. This skill encodes the two artifacts, the theme trap, and the navigation limitation.

When to use this skill

• The user wants to test a single Fragment without launching the full host Activity.
• A test crashes with IllegalArgumentException: You need to use a Theme.AppCompat theme (or descendant) with the design library and the fragment uses AppCompat / Material widgets.
• A test calls findNavController() and crashes with Fragment ... does not have a NavController set.
• The user wants to drive lifecycle (STARTED / RESUMED / DESTROYED) on a fragment for state-change testing.
• The user wants to inject a custom FragmentFactory for a fragment that doesn't have a no-arg constructor.
• The user mentions "headless fragment" or asks why onViewCreated doesn't fire.

When NOT to use this skill

• The host is an Activity, not a Fragment — see ../launching-activities-with-activityscenario/SKILL.md.
• The fragment requires a real navigation stack (NavHostFragment) — FragmentScenario does not provide one; use a custom test host activity that wires up NavHostFragment instead, or TestNavHostController.
• The runner / dependency stack is not yet set up — start with ../../runner/running-instrumented-tests-with-androidjunit4/SKILL.md.
• The fragment hosts Compose content and the test interacts via the Compose tree — see ../../../compose/setup/configuring-test-dependencies/SKILL.md.