Updating input html field from within an Angular 2 test

Question

I would like to change the value of an input field from within an Angular 2 unit test.

Answer 1

I also had trouble getting jonrsharpe's answer to work with Angular 2.4. I found that the calls to fixture.detectChanges() and fixture.whenStable() caused the form component to reset. It seems that some initialization function is still pending when the test starts. I solved this by adding extra calls to these methods before each test. Here is a snippet of my code:

beforeEach(() => {
    TestBed.configureTestingModule({
        // ...etc...
    });
    fixture = TestBed.createComponent(LoginComponent);
    comp = fixture.componentInstance;
    usernameBox = fixture.debugElement.query(By.css('input[name="username"]'));
    passwordBox = fixture.debugElement.query(By.css('input[type="password"]'));
    loginButton = fixture.debugElement.query(By.css('.btn-primary'));
    formElement = fixture.debugElement.query(By.css('form'));
});

beforeEach(async(() => {
    // The magic sauce!!
    // Because this is in an async wrapper it will automatically wait
    // for the call to whenStable() to complete
    fixture.detectChanges();
    fixture.whenStable();
}));

function sendInput(inputElement: any, text: string) {
    inputElement.value = text;
    inputElement.dispatchEvent(new Event('input'));
    fixture.detectChanges();
    return fixture.whenStable();
}

it('should log in correctly', async(() => {

    sendInput(usernameBox.nativeElement, 'User1')
    .then(() => {
        return sendInput(passwordBox.nativeElement, 'Password1')
    }).then(() => {
        formElement.triggerEventHandler('submit', null);
        fixture.detectChanges();

        let spinner = fixture.debugElement.query(By.css('img'));
        expect(Helper.isHidden(spinner)).toBeFalsy('Spinner should be visible');

        // ...etc...
    });
}));

Answer 2

The accepted solution didn't quite work for me in Angular 2.4. The value I had set was not appearing in the (test) UI, even after detectChanges() was called.

The way I got it to work was to set up my test as follows:

describe('TemplateComponent', function () {
  let comp: TemplateComponent;
  let fixture: ComponentFixture<TemplateComponent>;

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      imports: [ FormsModule ],
      declarations: [ TemplateComponent ]
    })
    .compileComponents();
  }));

  beforeEach(() => {
    fixture = TestBed.createComponent(TemplateComponent);
    comp = fixture.componentInstance;
  });

  it('should allow us to set a bound input field', fakeAsync(() => {
    setInputValue('#test2', 'Tommy');

    expect(comp.personName).toEqual('Tommy');
  }));

  // must be called from within fakeAsync due to use of tick()
  function setInputValue(selector: string, value: string) {
    fixture.detectChanges();
    tick();

    let input = fixture.debugElement.query(By.css(selector)).nativeElement;
    input.value = value;
    input.dispatchEvent(new Event('input'));
    tick();
  }
});

My TemplateComponent component has a property named personName in this example, which was the model property I am binding to in my template:

<input id="test2" type="text" [(ngModel)]="personName" />

Answer 3

You're right that you can't just set the input, you also need to dispatch the 'input' event. Here is a function I wrote earlier this evening to input text:

function sendInput(text: string) {
  inputElement.value = text;
  inputElement.dispatchEvent(new Event('input'));
  fixture.detectChanges();
  return fixture.whenStable();
}

Here fixture is the ComponentFixture and inputElement is the relevant HTTPInputElement from the fixture's nativeElement. This returns a promise, so you'll probably have to resolve it sendInput('whatever').then(...).

In context: https://github.com/textbook/known-for-web/blob/52c8aec4c2699c2f146a33c07786e1e32891c8b6/src/app/actor/actor.component.spec.ts#L134

---

Update:

We had some issues getting this to work in Angular 2.1, it didn't like creating a new Event(...), so instead we did:

import { dispatchEvent } from '@angular/platform-browser/testing/browser-util';

...

function sendInput(text: string) {
  inputElement.value = text;
  dispatchEvent(fixture.nativeElement, 'input');
  fixture.detectChanges();
  return fixture.whenStable();
}