Dart
The test package is Dart's standard testing library — used by both pure Dart projects and Flutter apps. It provides test(), group(), setUp(), tearDown(), async test support, stream matchers, and a rich set of built-in matchers. Everything in Flutter's flutter_test is built on top of
Test Automation
Mocking is the backbone of isolated unit testing. When your UserBloc depends on a UserRepository that hits a network, you don't want real HTTP calls in tests — you want a fake that returns exactly what you tell it to. Dart has two dominant mocking libraries: mockito (the established
Flutter
Mocking lets you replace real dependencies — HTTP clients, databases, sensors — with controlled fakes in tests. Dart has two excellent mocking libraries: Mockito (code-generation-based, type-safe) and Mocktail (no code gen, reflection-based). This guide covers both, with production-ready patterns for when/thenReturn, verify, argument matchers, and stubbing
Test Automation
Asynchronous code is everywhere in Dart — HTTP calls, file I/O, timers, isolates. Testing it correctly requires understanding how Dart's event loop works and how the flutter_test / test package interacts with it. This post goes deep on testing Future, Stream, Completer, time-sensitive code with fake_async,
Flutter
Flutter integration tests run your full app on a real device or emulator — no mocks, no shortcuts. This guide covers the integration_test package from scratch: setup, writing tests, managing app state between tests, running on CI, and gotchas that will save you hours of debugging. Key Takeaways * integration_test
Flutter
Flutter widget tests let you verify UI components in isolation — faster than integration tests, more reliable than manual checks. This guide covers the full flutter_test toolkit: testWidgets, WidgetTester, pump/pumpAndSettle, finders, and matchers with production-ready code examples. Key Takeaways * Widget tests run in a simulated environment — no emulator
Testing
Choosing a cross-platform mobile framework is partly a testing decision. The tools, ecosystems, and philosophies around testing differ significantly between Kotlin Multiplatform, React Native, and Flutter. This comparison helps you understand the tradeoffs before you commit. The Core Testing Philosophy Difference KMP shares business logic but keeps native UI.
Flutter
Flutter golden tests capture a screenshot of a widget and compare it pixel-by-pixel against a reference image (the "golden file"). If the screenshot changes, the test fails. This catches visual regressions — layout shifts, color changes, font differences — that behavioral tests miss entirely. This guide covers writing
Flutter
The bloc_test package provides blocTest() — a declarative test helper that makes BLoC and Cubit testing concise. You define the initial state, the events/actions to trigger, and the expected state sequence. Compared to manually subscribing to BLoC streams, blocTest() handles stream subscription, async operations, and teardown automatically. Key Takeaways
Flutter
Mocking in Flutter means replacing real dependencies (API clients, database repositories, platform services) with test doubles that you control. Mocktail is the modern choice: it doesn't require code generation, works with null safety out of the box, and has a clean API. Mockito is the alternative — it requires
Flutter
Flutter ships with three testing layers built into the SDK: unit tests (dart:test) for pure Dart logic, widget tests (flutter_test) for individual Flutter widgets in isolation, and integration tests (integration_test) for full app flows on a real device or emulator. This guide covers all three — setup, writing