Simulating a Service in Angular Using Karma and Jasmine for Testing

Question

Simulating a Service in Angular Using Karma and Jasmine for Testing

While attempting to simulate a service, I included it in the providers array within the spec and utilized createSpyObj with its functions. However, I encountered the following error:

Access to XMLHttpRequest at ''ng://DynamicTestModule/mycomponent_Host.ngfactory.js' from origin 'http:localhost:9876'

Can anyone identify what mistake I may be making?

// .... import the service

mockService = jasmine.createSpyObj(['function1'])
testBed.configureTestingModule({
  providers:[{
      {provide: myService, useValue: mockService}
  }]
}).compileComponents()

angular typescript unit-testing jasmine karma-jasmine

Answer 1

Answer №1

It appears that the way you constructed the spy is incorrect. The error suggests it may be due to an invalid import or another issue.

To correct this, follow these steps:

describe("UserDetailComponent", () => {
  let component: UserDetailComponent;
  let fixture: ComponentFixture<UserDetailComponent>;
  const mockUserService = jasmine.createSpyObj("UserSvcService", ["getUserDetail"]);

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [UserDetailComponent],
      providers: [
        { provide: UserSvcService, useValue: mockUserService }
      ]
    }).compileComponents();
  }));
....
...
 it('should set some values using service',()=>{
   mockUserService.getUserDetail.and.returnValue(
      of({ data: 'somevalue'})
    );
   expect(someCondition).toBeDefined();
 })
)}

There are alternative methods to achieve this, such as using Stubs and injecting them into the component with useClass. You can check out this article for more information.

Answer 2

It appears that the way you constructed the spy is incorrect. The error suggests it may be due to an invalid import or another issue.

To correct this, follow these steps:

describe("UserDetailComponent", () => {
  let component: UserDetailComponent;
  let fixture: ComponentFixture<UserDetailComponent>;
  const mockUserService = jasmine.createSpyObj("UserSvcService", ["getUserDetail"]);

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [UserDetailComponent],
      providers: [
        { provide: UserSvcService, useValue: mockUserService }
      ]
    }).compileComponents();
  }));
....
...
 it('should set some values using service',()=>{
   mockUserService.getUserDetail.and.returnValue(
      of({ data: 'somevalue'})
    );
   expect(someCondition).toBeDefined();
 })
)}

There are alternative methods to achieve this, such as using Stubs and injecting them into the component with useClass. You can check out this article for more information.

Answer 3

Answer №2

Imagine having a service named SharedService that needs testing.

// Import the service from the specified location using @
import { SharedService } from "@services"

// Create an instance within describe
let sharedService: SharedService

// Declare under providers in beforeEach
providers: [SharedService]

// Create the component and test fixture
fixture = TestBed.createComponent(yourComponentName);
component = fixture.componentInstance;
sharedService = fixture.debugElement.injector.get(SharedService)

// Use compileComponents only if not using webpack or angular CLI 

it('Should invoke MethodOne - sharedService ==> resolved', () => {
        let MockedData = {};
        spyOn(sharedService, 'someMethod').and.returnValue(Observable.of(MockedData));
        component.MethodOne();
        expect(sharedService.someMethod).toHaveBeenCalled();
    });

Answer 4

Imagine having a service named SharedService that needs testing.

// Import the service from the specified location using @
import { SharedService } from "@services"

// Create an instance within describe
let sharedService: SharedService

// Declare under providers in beforeEach
providers: [SharedService]

// Create the component and test fixture
fixture = TestBed.createComponent(yourComponentName);
component = fixture.componentInstance;
sharedService = fixture.debugElement.injector.get(SharedService)

// Use compileComponents only if not using webpack or angular CLI 

it('Should invoke MethodOne - sharedService ==> resolved', () => {
        let MockedData = {};
        spyOn(sharedService, 'someMethod').and.returnValue(Observable.of(MockedData));
        component.MethodOne();
        expect(sharedService.someMethod).toHaveBeenCalled();
    });

Answer 5

Answer №3

If you're looking to provide a service and customize each unit test's http response, Angular's HttpClientTestingModule and HttpTestingController can come in handy.

beforeEach(async(() => {
    TestBed.configureTestingModule({
        imports: [],
        providers: [SharedService]
    }).compileComponents();
}));

Once your service is set up, you have full access to its contents.

With these tools, you can create mock responses and use them tailored for each test. This flexibility allows you to configure specific HTTP responses for individual tests instead of applying the same one across your entire suite.

For instance:

it("should return valid response", fakeAsync(
   inject([HttpTestingController], (httpMock: HttpTestingController) => {
      let mockResponse = { success: true }

      httpMock.expectOne('endpoint name here').flush(mockResponse);

      fixture.whenStable().then(() => {
          //your acceptance criteria goes here
      });
   });
));

For more information, check out this helpful documentation: https://medium.com/netscape/testing-with-the-angular-httpclient-api-648203820712

Answer 6

If you're looking to provide a service and customize each unit test's http response, Angular's HttpClientTestingModule and HttpTestingController can come in handy.

beforeEach(async(() => {
    TestBed.configureTestingModule({
        imports: [],
        providers: [SharedService]
    }).compileComponents();
}));

Once your service is set up, you have full access to its contents.

With these tools, you can create mock responses and use them tailored for each test. This flexibility allows you to configure specific HTTP responses for individual tests instead of applying the same one across your entire suite.

For instance:

it("should return valid response", fakeAsync(
   inject([HttpTestingController], (httpMock: HttpTestingController) => {
      let mockResponse = { success: true }

      httpMock.expectOne('endpoint name here').flush(mockResponse);

      fixture.whenStable().then(() => {
          //your acceptance criteria goes here
      });
   });
));

For more information, check out this helpful documentation: https://medium.com/netscape/testing-with-the-angular-httpclient-api-648203820712

Simulating a Service in Angular Using Karma and Jasmine for Testing

Answer №1

Answer №2

Answer №3

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