Question

我有以下指令。当应用于input元素时，它会检查字符并在禁止该字符时调用preventDefault：

@Directive({
 selector: '[cdtPreventInput]'
})
  export class PreventInputDirective implements OnInit {

  // the list of characters that are to be prevented
  @Input() cdtPreventInput: String;

  constructor() { }

  ngOnInit() {
    if (!this.cdtPreventInput) {
      throw new Error('cdtPreventInput cannot be used without providing a 
          list of characters.');
    }
  }

 @HostListener('keypress', ['$event']) onKeyPress(event) {
   if (_.includes(this.cdtPreventInput.split(','), event.key)) {
    event.preventDefault();
  }
}

工作正常，但我无法弄清楚如何测试它。到目前为止，我有以下内容：

describe('PreventInputDirective', () => {
  let fixture;
  let input: DebugElement;

  beforeEach(() => {
    fixture = TestBed.configureTestingModule({
      declarations: [PreventInputDirective, TestComponent]
    }).createComponent(TestComponent);

    input = fixture.debugElement.query(By.directive(PreventInputDirective));
  });

  it('should create an instance', () => {
    const directive = new PreventInputDirective();
    expect(directive).toBeTruthy();
  });

 it('should prevent default keypress event', () => {
    const event = new KeyboardEvent('keypress', {
      'key': '.'
    });
     input.nativeElement.dispatchEvent(event);

     expect(input.nativeElement.value).toEqual('');
  });

  @Component({
    template: `<input cdtPreventInput="." />`
  })
  class TestComponent { }
});

虽然不行。按键事件未触发。知道如何测试这个指令吗？

Answer 1

我找到了解决方案。我只是检查事件的defaultPrevented属性，而不是检查值（永远不会改变）。

我也错过了两件事：

fixture.detectChanges（）;在beforeEach
事件应该可以取消

这是完整的测试：

 describe('PreventInputDirective', () => {
  let fixture;
  let input: DebugElement;

  beforeEach(() => {
    fixture = TestBed.configureTestingModule({
      declarations: [PreventInputDirective, TestComponent]
    }).createComponent(TestComponent);

    input = fixture.debugElement.query(By.directive(PreventInputDirective));
    fixture.detectChanges();
  });

  it('should create an instance', () => {
    const directive = new PreventInputDirective();
    expect(directive).toBeTruthy();
  });

  it('should prevent keypress event', () => {
    const event = new KeyboardEvent('keypress', {
      'key': '.',
      cancelable: true
    });

    input.nativeElement.dispatchEvent(event);
    expect(event.defaultPrevented).toBeTruthy();
  });

  it('should not prevent keypress event', () => {
    const event = new KeyboardEvent('keypress', {
      'key': '5',
      cancelable: true
    });

    input.nativeElement.dispatchEvent(event);
    expect(event.defaultPrevented).toBeFalsy();
  });

  @Component({
    template: `<input cdtPreventInput="." />`
  })
  class TestComponent { }
});

Angular如何测试@HostListener

1 个答案: