Tips for crafting a test scenario for input alterations within Angular

Hello there, currently I am working on an application using Angular and TypeScript.

Here is a snippet of my template code:

<input type="text" placeholder="Search Results" (input)="searchInput($event)">

And here is the TypeScript code for the searchInput method :

searchInput(event: Event & { target: HTMLInputElement}) {
   const { value } = event.target;
   this.value = value;
    // calling another method to reset values
  }

I am now trying to figure out how to write input test cases in my spec.ts file.

describe('Component', () => {
  let component: Component;
  let fixture: ComponentFixture<Component>;
  const event = Event; // Is this correct ?
  beforeEach(async(() => {
    TestBed.configureTestingModule({
      imports: [
          AppModule
      ],
      providers: [
      ]
    })
    .compileComponents();
  }));

  beforeEach(() => {
    fixture = TestBed.createComponent(Component);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

  it('test case for searchInput() ', () => {
    // what would be the best approach here?
  });
});

I would appreciate any guidance on how to go about writing these test cases. Thank you!

Answer №1

When it comes to creating a straightforward test case, here is one method that can be used.

Here's a breakdown of what this test does:

  1. It initializes the component
  2. Verifies that the default value for value is falsy
  3. Finds the specific HTML input element using CSS (additional specificity may be required based on your template)
  4. Sets the input element's value and triggers an input event
  5. Ensures that the value has been correctly updated

Code Example (don't forget to import By):

...    

import { By } from '@angular/platform-browser';

...

it('searchInput should update value when input changes', async(() => {
    const fixture = TestBed.createComponent(AppComponent);

    expect(fixture.debugElement.nativeElement.value).toBeFalsy()

    const el: HTMLInputElement = fixture.debugElement.query(By.css('input')).nativeElement;
    const testValue = 'some_value';

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

    expect(fixture.componentInstance.value).toEqual(testValue);
}));

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