Testing Android MVVM Without Mocks

StateFlow with SharingStarted.WhileSubscribed doesn't emit until there's an active subscriber — tests need backgroundScope.launch { vm.flow.collect {} } or the flow never starts
In-memory fakes (a MutableMap + MutableStateFlow) beat MockK for ViewModel tests: you test real state transitions, not just that a method was called
StandardTestDispatcher + advanceUntilIdle() gives you deterministic control over coroutines — no delay(), no flaky timing
Writing the fakes also exposed bugs — the TrashViewModel was creating a new MutableStateFlow() on every getDeletedNotes() call instead of returning the same flow, so upstream emissions never reached the ViewModel
38 passing JVM tests, no device required, runs in ~3 seconds on CI