Within an Angular test scenario, execute a static method from a service that triggers an HTTP get request to fetch stored JSON data. This data is then retrieved and returned back to the service

Currently, I am facing a challenge in my Angular test case where I am trying to load JSON data via an HTTP call.

  • The issue arises when a static method is called from a service spec file named "url-service.spec" to another service named "load-json.service.spec".
  • In the "load-json.pservice.spec" service, an HTTP get request is made to fetch the JSON data, and the subscription happens within that method. The JSON data is then returned, but it does not return an observable back to url-service.

I have tried using spyOn for calling the static method, but I am struggling to inject HTTP, load the JSON, and subscribe within that context.

Any guidance or assistance on this matter would be greatly appreciated. Thank you in advance!

javascriptangulartypescriptjasmine

Answer №1

Allow me to provide an illustration from a recent project of mine. This example could potentially give you some insights.

describe("Employee feedback platform", () => {
let httpServiceMock: jasmine.SpyObj<HttpClient>;
let feedbackPlatform: FeedbackPlatform;

 beforeEach(() => {
 const apiEndpointServiceSpy = jasmine.createSpyObj('ApiEndpointBuilderService', ['buildApiResponse']);
 httpServiceMock = jasmine.createSpyObj('HttpClient', ['patch']);
feedbackPlatform = new FeedbackPlatform(httpServiceMock, apiEndpointServiceSpy);
});

it('should submit employee feedback and receive confirmation response', (done: DoneFn) => {
const expectedConfirmationData: ConfirmationData = { id: 5678, message: "Feedback submitted successfully" };

httpServiceMock.patch.and.returnValue(asyncData(expectedConfirmationData));

 feedbackPlatform.submitEmployeeFeedback(9876, "Positive feedback for team leader").subscribe({
  next: confirmData => {
    expect(confirmData).withContext("Anticipating confirmation data").toEqual(expectedConfirmationData);
    done();
  },
  error: done.fail
});

 expect(httpServiceMock.patch.calls.count()).withContext('one call').toBe(1);   
});   
});

Answer №2

You may need to approach the problem differently as it seems you are heading in the wrong direction. I recommend mocking the method found in "load-json.service.ts". The mocked method should accurately return the JSON data.

If you are conducting tests on certain components, here is a suggestion that might be helpful.

Pay attention to the providers section where we are instructing the component to utilize our mocked LoadJsonService.

...
const jsonDataObj = {foo: 'bar'};
const mockedLoadJsonService = {
  getJson:()=> JSON.stringify(jsonDataObj)
}

beforeEach(async () => {
    await TestBed.configureTestingModule({
      imports: [
        ...
      ],
      declarations: [...],
      providers: [
        { provide: LoadJsonService, useValue: mockedLoadJsonService },
      ],
    }).compileComponents();
  });

...

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