First Hilt-injected ViewModel + sealed UiState pattern.
LibraryUiState (sealed interface): Loading / Empty / Success / Error.
The cases are exhaustive so Compose `when` blocks the compiler checks.
LibraryViewModel:
- combine(observeArtists, observeAlbums) → Success/Empty decision
- .catch translates upstream Flow exceptions to UiState.Error
- .stateIn(viewModelScope, WhileSubscribed(5_000), Loading) — the
standard Compose-friendly pattern; subscriptions tear down 5s after
the last collector to ride out config changes without hanging the
DAO Flow forever.
MainDispatcherExtension — JUnit 5 equivalent of the JUnit 4
MainDispatcherRule pattern (audit-deferred item; trigger met). Swaps
Dispatchers.Main for UnconfinedTestDispatcher in beforeEach +
resetMain in afterEach. Apply with `@ExtendWith`.
LibraryViewModelTest covers all four UiState cases — initial Loading,
empty cache (Empty), populated cache (Success), and an upstream Flow
exception (Error). MockK for the repo, Turbine for the Flow assertions.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
bvandeusen
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