Unable to simulate keypress event in Angular 2 unit test (Jasmine)

Question

I am using a directive to get the data from input used as a filter text.

here is my hostlistener in the directive:

@HostListener('input', ['$event.target.value'])
  public onChangeFilter(event: any): void {
    console.log('input event fired, value: ' + event);
    this.columnFiltering.filterString = event;
    this.filterChanged.emit({filtering: this.columnFiltering});
  }

this code is working perfectly, I am unable to unit test the same.

I have subscribed to the filterChanged EventEmitter, in my unit test to check the value.

I tried simulating keypress event to change value and also tried settings value attribute. None of these is working for me.

here is my spec file:

describe('Table View', () => {
  let fixture: ComponentFixture<any>;
    let context: TableComponent;
   beforeEach(() => {
     TestBed.configureTestingModule({
          providers: [
            TableComponent,
          ],
          imports: [TableModule],
      });
      fixture = TestBed.createComponent(TableComponent);
      context = fixture.componentInstance;
    });
it('should allow filter', () => {
      const element = fixture.nativeElement;
      context.config = config;
      fixture.detectChanges();

      let tableChangeCount = 0;
      let tableEvent: any;
      context.tableChanged.subscribe((event: any) => {
        tableChangeCount++;
        tableEvent = event;
      });
      // Check if table exists
      let inputElement = element.querySelectorAll('tr')[1].querySelector('input');
    let e = new KeyboardEvent("keypress", {
            key: "a",
            bubbles: true,
            cancelable: true,
          });
          inputElement.dispatchEvent(e);
 });

});

I tried setting value:

let attrs = inputElement.attributes;
      inputElement.setAttribute('value', 'abc');
       for (let i = attrs.length - 1; i >= 0; i--) {
         // Attribute value is set correctly
         if (attrs[i].name === 'value') {
         console.log(attrs[i].name + "->" + attrs[i].value);
         }
       }

Can anyone please help me, how can I unit test the same?

Solution 1

I've had some trouble simulating a keypress in a unit test also. But came across an answer by Seyed Jalal Hosseini. It might be what you're after.

If you're attempting to simulate a keypress you can trigger an event by calling dispatchEvent(new Event('keypress')); on the element.

Here is the answer I'm referring to which gives more detail : https://stackoverflow.com/a/37956877/4081730

If you want to set the key that was pressed, this can be done also.

const event = new KeyboardEvent("keypress",{
    "key": "Enter"
});
el.dispatchEvent(event);

Further information I've just come across: https://developer.mozilla.org/en-US/docs/Web/Guide/Events/Creating_and_triggering_events

Solution 2

If you wish to use a key code (or "which"), you can do this:

// @HostListener('document:keypress')

const escapeEvent: any = document.createEvent('CustomEvent');
escapeEvent.which = 27;
escapeEvent.initEvent('keypress', true, true);
document.dispatchEvent(escapeEvent);

Solution 3

it('should trigger a TAB keypress event on an element', () => {
    const tabKeypress = new KeyboardEvent('keypress', {
      // @ts-ignore
      keyCode: 9, // Tab Key
      cancelable: true
    });
const myTableEle = debugEle.nativeElement.querySelector('.your-element');
    myTableEle.dispatchEvent(tabKeypress);
    fixture.detectChanges();
});

// @ts-ignore :- is to remove TS warning because keyCode is deprecated. Its not needed in case you want to set "key" property of KeyboardEvent.