android-tdd

Use runTest for all suspend functions and inject a CoroutineDispatcher into the ViewModel instead of hardcoding Dispatchers.Main. Replace Main with a MainDispatcherRule using StandardTestDispatcher, and pass the rule's dispatcher into runTest so both share one TestCoroutineScheduler.

Prefer hand-written fakes that implement the real interface with in-memory behavior over mocking frameworks like MockK. Fakes are reusable, readable, and test behavior rather than implementation. Use mocks only when verifying a specific interaction is the behavior under test, such as analytics events.

Hot flows like StateFlow never complete, so collecting them directly on the TestScope hangs until the 60-second timeout. Use Turbine's test {} block, which collects and cancels automatically, or launch the collector on backgroundScope which is auto-cancelled at test end.

Unit tests in src/test run on the JVM for pure logic like ViewModels and UseCases. Robolectric tests also run on the JVM but simulate Android for Room DAOs and Context-dependent code. Instrumented tests in src/androidTest run on a device or emulator for Compose UI and end-to-end flows.

Prefer semantics-first finders like onNodeWithText and onNodeWithContentDescription because they assert what users actually see and exercise accessibility. Reserve onNodeWithTag for cases with no stable user-visible text, such as lists of identical rows or locale-dependent copy.

The framework's InfiniteAnimationPolicy cancels indeterminate animations when the test clock auto-advances. Set mainClock.autoAdvance = false before setContent, then drive frames manually with advanceTimeByFrame() and advanceTimeBy(durationMillis).