What is the best approach for creating a basic test to evaluate the functionality of MatDialog in Angular 2?

I'm currently working on a component that looks like this:

@Component({
  selector: 'my-form',
  templateUrl: './my-form.component.html',
})
export class MyFormComponent implements OnInit {

  @Input('company') company: CompanyInfo;
  private config: ConfigInterface | null;

  constructor(private companyService: CompanyService, private something: Something, private dialog: MatDialog) {
  }
  ngOnInit() {
    ....
  }

  theFunctionToBeTested(company: string) {
    if (someTest.indexOf(domain)) {
      this.dialog.open(MyAllertComponent, {
        data: {
          title: 'blah',
        },
      });
    }
  }
}

However, my unit test is not performing as expected:

describe( 'MyFormComp', () => {
  it('should open MatDialog if email is from popular domain', () => {
    const dialog = {} as MatDialog;
    const comp = new MyComponent({} as CompanyService, {} as Something, dialog);
    comp.getCompanys(company);
    expect(dialog.open(AlertComponent));
  });
})

And I'm receiving the following error message:

TypeError: dialog.open is not a function

I am aware of the reason behind this error - I need to mock the dialog properly for the open function to work. Can someone guide me on how to achieve this using jasmine (i.e. how to correctly mock MatDialog?)

Since I am new to JavaScript unit testing, I would appreciate more specific guidance rather than just general keywords to search for.

Answer №1

If you want to create spies for your component dependencies, you can utilize the beforeEach method like this:

emailServiceSpy = jasmine.createSpyObj('EmailService', {});
somethingSpy = jasmine.createSpyObj('Something', {});
dialogSpy = jasmine.createSpyObj('MatDialog', ['open']);

Next, make sure to provide these spies in your TestModule:

TestBed.configureTestingModule({
  declarations: [YourComponent],
  providers: [
    { provide: EmailService, useValue: emailServiceSpy },
    { provide: Something, useValue: somethingSpy },
    { provide: MatDialog, useValue: dialogSpy },
  ],
  imports: [],
}).compileComponents();

Finally, in your test case, you can verify if your spy functions are being called:

expect(dialogSpy.open).toHaveBeenCalled();

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