Testing - Can't resolve all parameters for (ClassName)

Question

Context

I created an ApiService class to be able to handle our custom API queries, while using our own serializer + other features.

ApiService's constructor signature is:

constructor(metaManager: MetaManager, connector: ApiConnectorService, eventDispatcher: EventDispatcher); 

• MetaManager is an injectable service that handles api's metadatas.
• ApiConnectorService is a service which is wrapping Http to add our custom headers and signature system.
• EventDispatcher is basically Symfony's event dispatcher system, in typescript.

Problem

When I test the ApiService, I do an initialization in beforeEach:

beforeEach(async(() => {     TestBed.configureTestingModule({         imports  : [             HttpModule         ],         providers: [             ApiConnectorService,             ApiService,             MetaManager,             EventDispatcher,             OFF_LOGGER_PROVIDERS         ]     }); })); 

and it works fine.

Then I add my second spec file, which is for ApiConnectorService, with this beforeEach:

beforeEach(async(() => {     TestBed.configureTestingModule({         imports  : [HttpModule],         providers: [             ApiConnectorService,             OFF_LOGGER_PROVIDERS,             AuthenticationManager,             EventDispatcher         ]     }); })); 

And all the tests fail with this error:

Error: Can't resolve all parameters for ApiService: (MetaManager, ?, EventDispatcher).

• If I remove api-connector-service.spec.ts (ApiConnectorService's spec file) from my loaded tests, ApiService's tests will succeed.
• If I remove api-service.spec.ts (ApiService's spec file) from my loaded tests, ApiConnectorService's tests will succeed.

Why do I have this error? It seems like the context between my two files are in conflict and I don't know why and how to fix this.

Answer 1

Using Jest?

In case anyone gets here AND you're using Jest to test your Angular app (hopefully we're a growing minority), you will run into this error if you are not emitting decorators ("emitDecoratorMetadata":true). You'll need to update your tsconfig.spec.json file so it looks like:

{   "extends": "../../tsconfig.json",   "compilerOptions": {     "emitDecoratorMetadata": true,     "outDir": "../../out-tsc/spec",     "types": [       "jest",       "node"     ]   },   "files": [   ],   "include": [     "**/*.spec.ts",     "**/*.d.ts"   ] }