Angular unit test input value

Question

I have been reading official Angular2 documentation for unit testing (https://angular.io/docs/ts/latest/guide/testing.html) but I am struggling with setting a component's input field value so that its reflected in the component property (bound via ngModel). The screen works fine in the browser, but in the unit test I cannot seem to be able to set the fields value.

I am using below code. "fixture" is properly initialized as other tests are working fine. "comp" is instance of my component, and the input field is bound to "user.username" via ngModel.

it('should update model...', async(() => {
    let field: HTMLInputElement = fixture.debugElement.query(By.css('#user')).nativeElement;
    field.value = 'someValue'
    field.dispatchEvent(new Event('input'));
    fixture.detectChanges();

    expect(field.textContent).toBe('someValue');
    expect(comp.user.username).toBe('someValue');
  }));

My version of Angular2: "@angular/core": "2.0.0"

Answer 1

Inputs don't have textContent, only a value. So expect(field.textContent).toBe('someValue'); is useless. That's probably what's failing. The second expectation should pass though. Here's a complete test.

@Component({
  template: `<input type="text" [(ngModel)]="user.username"/>`
})
class TestComponent {
  user = { username: 'peeskillet' };
}

describe('component: TestComponent', () => {
  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [FormsModule],
      declarations: [ TestComponent ]
    });
  });

  it('should be ok', async(() => {
    let fixture = TestBed.createComponent(TestComponent);
    fixture.detectChanges();
    fixture.whenStable().then(() => {
      let input = fixture.debugElement.query(By.css('input'));
      let el = input.nativeElement;

      expect(el.value).toBe('peeskillet');

      el.value = 'someValue';
      el.dispatchEvent(new Event('input'));

      expect(fixture.componentInstance.user.username).toBe('someValue');
    });
  }));
});

The important part is the first fixture.whenStable(). There is some asynchronous setup with the forms that occurs, so we need to wait for that to finish after we do fixture.detectChanges(). If you are using fakeAsync() instead of async(), then you would just call tick() after fixture.detectChanges().

Answer 2

Just add

fixture.detectChanges();

fixture.whenStable().then(() => {
  // here your expectation
})

Answer 3

Use your expect/assert within the whenStable.then function like this:

component.label = 'blah';
fixture.detectChanges();

fixture.whenStable().then(() => {
    expect(component.label).toBe('blah');
}