I am building a really modular application, but I have no idea how to write unit tests for the architectural glue code. I know how to test a service or a component, but how do I verify that my dependency injection setup is working or that my Facade is correctly calling the service? Any advice?
Architectural glue code is verified by using TestBed to resolve dependency injection containers and mocking service dependencies within Facades to validate interaction contracts and data orchestration.
1 answer
Testing architectural glue code requires shifting focus from internal component logic to verifying the interaction contracts between your dependency injection containers and Facades. You can validate your wiring by creating integration-level unit tests that resolve these dependencies within a controlled TestBed context.
To verify that your Facade is correctly invoking the underlying services, instantiate the Facade within a test block and use jasmine.createSpyObj to mock the injected service dependencies. This allows you to inspect the call stack and ensure that the Facade is passing the correct arguments to the service methods. You should be asserting that the internal orchestrator logic correctly maps the data before reaching the service layer.
Testing your dependency injection setup involves confirming that your token providers are correctly resolved during the module initialization phase. By creating a setup function that initializes the Angular TestBed with your specific providers, you can verify that the expected instances are injected into your class constructors. If you rely on custom tokens or multi-providers, assert the length and content of the resolved array to ensure the injector is configured as expected.
