feat(services): add example of jasmine spy stubbing

Author: juristr

README.md

@@ -43,6 +43,8 @@ All the scenarios are listed here below and nicely linked to the source file.
       _Learn how to test async operations using the `async()` as well as `fakeAsync()` functions._
     * [Mocking and remote http calls](./src/app/services/remote.service.spec.ts)
       _Learn how to mock external dependencies, such as use the `MockBackend` provided by Angular to respond to http calls._
+    * [Mocking remote calls with Jasmine spies](./src/app/services/remote.service.fake-call.spec.ts)
+      _Fake the call by using Jasmine spies._
 1.  [**Testing Pipes**](./src/app/pipes)
     * [custom filter pipe](./src/app/pipes/filter.pipe.spec.ts)
     * [async pipes within templates](./src/app/components/async-stream.component.spec.ts)  

src/app/services/remote.service.fake-call.spec.ts

@@ -0,0 +1,55 @@
+/* tslint:disable:no-unused-variable */
+
+import {
+  HttpClientTestingModule,
+  HttpTestingController
+} from '@angular/common/http/testing';
+import { of } from 'rxjs/observable/of';
+import { TestBed } from '@angular/core/testing';
+import { RemoteService } from './remote.service';
+
+describe('RemoteService (fake call with Jasmine)', () => {
+  let service: RemoteService;
+
+  beforeEach(() => {
+    TestBed.configureTestingModule({
+      imports: [HttpClientTestingModule],
+      // providers: [{ provide: RemoteService, useValue: jasmineSpy }]
+      providers: [RemoteService]
+    });
+
+    // inject the service
+    service = TestBed.get(RemoteService);
+  });
+
+  it('should have a service instance', () => {
+    expect(service).toBeDefined();
+  });
+
+  it('should return the mocked data in the subscribe', () => {
+    const spy = spyOn(service, 'fetchViaHttp').and.returnValue(
+      of({
+        name: 'Juri'
+      })
+    );
+
+    // act
+    service.fetchViaHttp().subscribe(data => {
+      expect(data.name).toBe('Juri');
+    });
+
+    // assert
+    expect(spy).toHaveBeenCalled();
+  });
+
+  it('should not invoke the error throwing function since we mocked it', () => {
+    const emptyFn = () => {};
+    const spy = spyOn(service, 'throwingError').and.callFake(emptyFn);
+
+    // act
+    service.throwingError();
+
+    // assert
+    expect(spy).toHaveBeenCalled();
+  });
+});

src/app/services/remote.service.ts

@@ -9,4 +9,8 @@ export class RemoteService {
   fetchViaHttp(): Observable<any> {
     return this.http.get('/someendpoint/people.json');
   }
+
+  throwingError() {
+    throw new Error('Should be mocked');
+  }
 }