Your ViewModel Tests Shouldn’t Need Android

A guide to testing Android ViewModels without Android framework dependencies by extracting UI logic into a pure Kotlin UIModel class. The pattern injects a CoroutineScope into the UIModel constructor, allowing tests to pass backgroundScope from runTest instead of using Dispatchers.setMain(). Key techniques include using fun interfaces for use cases to create simple lambda-based fakes without mock libraries, a createSut helper pattern for test setup, and using UnconfinedTestDispatcher for synchronous-looking tests. The post also explains why WhileSubscribed(5_000) is preferred over Eagerly for resource efficiency, and covers gotchas like StateFlow conflation and advanceUntilIdle() not processing backgroundScope tasks.