factory-function-composition

Use factory functions for dependency injection by passing external clients into a function, allowing you to compose services with proper separation of concerns and inject mock dependencies for testing.

Separating client configuration from service logic is best achieved using factory function patterns, which ensure client, service, and method-specific options remain distinct and manageable.

Refactor a service creating its own database client by applying factory function composition to inject the client as a dependency, making the service testable and reusable with different configurations.

Yes, you can wrap external resources with domain-specific methods using factory functions, which provides a universal signature for dependency injection and cleanly manages configuration.

Mixing client and service options makes code hard to test because dependencies are tightly coupled and hidden internally, preventing the injection of mock clients needed for isolated unit tests.

Avoid factory function composition for service creation when dealing with simple, stateless utilities that have no external dependencies or configuration requirements to manage.