Difficulty Mocking Dependency Injection in Angular Unit Tests with HttpClient
I'm facing a challenge with unit testing a component in Angular that relies on an injected HttpClient to fetch data from an API. The component looks like this: ```typescript import { Component, OnInit } from '@angular/core'; import { HttpClient } from '@angular/common/http'; import { Observable } from 'rxjs'; @Component({ selector: 'app-data-fetcher', templateUrl: './data-fetcher.component.html' }) export class DataFetcherComponent implements OnInit { data: any; constructor(private http: HttpClient) { } ngOnInit(): void { this.fetchData(); } fetchData(): void { this.http.get('https://api.example.com/data') .subscribe(response => this.data = response); } } ``` In my test file, I attempted to mock the HttpClient using Jasmine's `createSpyObj`, but I'm running into issues with how the observables are subscribed. Here’s what I’ve tried so far: ```typescript import { ComponentFixture, TestBed } from '@angular/core/testing'; import { HttpClientTestingModule, HttpTestingController } from '@angular/common/http/testing'; import { DataFetcherComponent } from './data-fetcher.component'; describe('DataFetcherComponent', () => { let component: DataFetcherComponent; let fixture: ComponentFixture<DataFetcherComponent>; beforeEach(async () => { await TestBed.configureTestingModule({ imports: [HttpClientTestingModule], declarations: [DataFetcherComponent] }).compileComponents(); }); beforeEach(() => { fixture = TestBed.createComponent(DataFetcherComponent); component = fixture.componentInstance; }); it('should fetch data on init', () => { const httpMock = TestBed.inject(HttpTestingController); component.ngOnInit(); const req = httpMock.expectOne('https://api.example.com/data'); expect(req.request.method).toBe('GET'); req.flush({ message: 'success' }); fixture.detectChanges(); expect(component.data).toEqual({ message: 'success' }); }); }); ``` However, I keep getting the error: `Expected one matching request for criteria “Get is https://api.example.com/data”, found none.` I've ensured that the URL is correct and that I'm flushing the mock response, but it seems like the request isn't being captured. Can anyone provide insights on what I might be missing or if there's a better way to structure this test? I'm using Angular 13.0.0 and Jasmine 3.9.0. Thanks! Thanks in advance!