eng-define-service-boundary

To ensure deterministic testing, define service boundaries by introducing Dart interfaces for side effects like database access or file I/O. This isolates impure operations, keeping your core functions pure and your tests reliable and reproducible.

Use Riverpod for dependency injection by defining a Dart interface for database access, implementing it with a live class, and wiring that implementation as a provider in your application's main entry point to enforce clear service boundaries.

The best way to isolate side effects like local notifications is to define clear Dart interfaces acting as service boundaries. This separates impure operations from pure functions, enabling clean maintenance and deterministic test execution.

Yes, you need Dart interfaces to create deterministic fakes for file I/O services. Interfaces define the service boundaries, allowing you to substitute live implementations with fakes during testing to prevent side effects from affecting pure functions.

You should introduce side-effect boundaries for persistence and notifications when implementing features that require these services. Defining boundaries early ensures the surrounding code remains pure, making it easier to manage and test deterministic fakes.