Angular2 FormBuilder unit testing

Question

I have two question in regards to mocking Formbuilder in Angular2.

1) How do I mock formBuilder in a spec? Are there any given mocks that we can use? I would like to for instance, update the values of a form in my spec, and then test to see if the form is still valid - or test the functionality of methods in my component that update a formbuilder group, or determine if a formbuilder group is valid.

2) How do I deal with the following error given that fb is a DI injection of Formbuilder in a spec?

null is not an object (evaluating 'this.fb.group')

when the component is as follows:

export class LoginComponent implements OnInit {
  constructor( private fb: FormBuilder ) {}

  ngOnInit() {
    this.loginForm = this.fb.group({
      'email': this.user.email,
      'password': this.user.password
    });
  }
}

Answer 1

I actually build a new instance of FormBuilder and give it to component under testing.

sut = new LoginComponent(service, new FormBuilder());

If you want to modify any control that belongs to your ControlGroup/FormGroup then you can do it in following manner:

(<Control>sut.loginForm.controls['Name']).updateValue('Jon Doe');

You can test validity as well:

sut.loginForm.valid

Update:

describe('Component', () => {
  let sut: Component;
  let service: Service;

  beforeEach(() => {
    service = new Service(null);
    sut = new Component(new FormBuilder(), service);
        });

  it('should have object initialized', () => {
    expect(sut.selectedBankAccount).toBeDefined();
  });
...

Answer 2

If you are using the newest version of Angular2, and want to use their testbed, here is a working spec.

describe('Login Component', () => {
  let comp: LoginComponent;
  let fixture: ComponentFixture<LoginComponent>;

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [LoginComponent],
      providers: [
        FormBuilder
      ]
      }).compileComponents()
      .then(() => {
        fixture = TestBed.createComponent(LoginComponent);
        comp = fixture.componentInstance;
      });
  }));

  it('user should update from form changes', fakeAsync(() => {
    const testUser = {
      email: '[email protected]',
      password: '12345'
    };
    comp.loginForm.controls['email'].setValue(testUser.email);
    comp.loginForm.controls['password'].setValue(testUser.password);
    expect(comp.user).toEqual(testUser);
  }));
});