angular-di

Angular dependency injection with the inject() API replaces constructor parameters by obtaining dependencies inside property initializers. This approach simplifies dependencies, centralizes provider management, and makes unit testing easier by removing verbose constructor signatures.

Angular InjectionToken providers are used to decouple interface implementations from concrete classes. You should use token-based provisioning when configuring shared services or environment variables across large apps, allowing flexible implementation swapping without modifying consumer components.

Singleton providers share a single instance across the entire application, while scoped providers create per-component or per-route lifecycles. Angular hierarchical injection controls these scopes by configuring providers at root, component, or route levels to manage state isolation appropriately.

EnvironmentInjector enables advanced dependency injection patterns by establishing dynamic injection contexts. You use runInjectionContext to execute functions within a specific injector scope, allowing runtime creation of providers and components outside standard static configurations.

Yes, Angular DI testing supports multi providers and token mocks to verify dependency injection configurations. You can assert provider overrides, simulate token-based dependencies, and test scoped provider lifecycles to ensure components receive correct service instances.

Angular dependency injection allows route-level providers by configuring scoped providers within route definitions. This leverages the hierarchical injector to create isolated service instances per route, controlling singleton versus per-component lifecycles without polluting the root environment injector.