Testing
PITest (PIT) is the dominant mutation testing framework for JVM languages. While most documentation targets Maven/Java setups, PITest works equally well with Gradle and Kotlin — with a few configuration differences worth knowing about. This guide covers the complete Gradle setup, Kotlin-specific behavior, and how to get meaningful results
Testing
ViewModels are the core of Android architecture: they hold state, handle business logic, and expose data via Kotlin Flow. Testing them thoroughly — including loading states, error handling, and side effects — requires understanding how to control coroutines and observe Flow emissions in tests. This guide covers ViewModel testing with TestDispatcher, Turbine
Kotlin
Espresso is Android's UI testing framework, executing tests directly on a device or emulator. This guide covers the full Espresso toolkit: ViewMatchers for finding views, ViewActions for interacting, ViewAssertions for validating state, IdlingResources for async synchronization, and Hilt for injecting test dependencies. Unit tests tell you your logic
Android
Room is Android's recommended database library, wrapping SQLite with type-safe query builders and Kotlin coroutines support. Testing Room properly means validating DAO queries, schema migrations, and Paging 3 integration—without ever touching a real disk database. Room Testing Strategy Room provides first-class support for testing through
Android
Kotlin Flow is the standard for reactive programming in Android—but testing asynchronous streams is notoriously awkward. Turbine is Cash App's library that makes Flow testing readable and deterministic. Instead of manual coroutine collection and timing hacks, you get clean, sequential assertions. Why Testing Flows Is Hard Without
Android
Koin is the lightweight dependency injection framework that dominates Android Kotlin projects. Unlike Dagger/Hilt which uses code generation, Koin operates at runtime—which means misconfigured modules fail at startup rather than compile time. Testing your Koin setup properly catches these failures before they hit production. Why Koin Testing Matters
Android
Retrofit is Android's de facto HTTP client library. Testing it properly means validating that your API service interfaces produce correct requests, handle error responses gracefully, and work with your custom call adapters and interceptors. OkHttp's MockWebServer is the tool that makes all of this possible. Why
Android
Ktor is JetBrains' official HTTP client for Kotlin Multiplatform—used in KMP projects, pure JVM backends, and Android applications. Unlike Retrofit, which wraps OkHttp, Ktor has its own engine abstraction that makes testing particularly clean: just swap the real engine for MockEngine and control every response. Why Ktor Testing
Android
Jetpack Compose replaces the View hierarchy with a declarative composable tree—and that changes how you test Android UIs. Traditional Espresso tests targeting View IDs don't work. Instead, Compose provides a dedicated testing API built around the semantic tree, enabling more robust and readable tests that aren'
Testing
TalkBack is Android's built-in screen reader, and testing it manually doesn't scale across a large test suite. Espresso's AccessibilityChecks API, the Accessibility Test Framework, and Robolectric together give you a layered approach to catching accessibility regressions in CI before they reach users. Android&
Testing
Compose Multiplatform extends Jetpack Compose beyond Android, bringing the same declarative UI model to iOS, desktop (macOS, Windows, Linux), and web. But testing a UI that runs on four platforms is a different challenge than testing a single-platform app. This guide covers how to write and run Compose Multiplatform
Testing
Kotlin Multiplatform (KMP) lets you write business logic once and share it across Android, iOS, desktop, and web. But sharing code means shared bugs — and shared testing responsibilities. This guide covers everything you need to test KMP projects effectively. Why Testing KMP Is Different In a typical Android project, your