测试来自 Angular Reactive 表单的提交数据

Question

基于https://angular.io/guide/reactive-forms 中的第一个示例，我创建了以下哑组件：

@Component({
  selector: 'app-name-editor',
  templateUrl: './name-editor.component.html',
  styleUrls: ['./name-editor.component.css']
})
export class NameEditorComponent {

  name = new FormControl('');

  @Output('submitted') submitted = new EventEmitter<string>();

  onSubmit() { this.submitted.emit(this.name.value); }
}

... 我想为此编写一个单元测试来验证是否提交了一个值。这使用了 https://angular.io/guide/testing#component-inside-a-test-host 中建议的 TestHost ：

@Component({
  template: `
     <app-name-editor (submitted)=onSubmit($event)>
     </app-name-editor>
   `})
class TestHostComponent {
  submitted: string;
  onSubmit(data: string) { this.submitted = data; }
}

describe('NameEditorComponent', () => {
  let testHost: TestHostComponent;
  let fixture: ComponentFixture<TestHostComponent>;
  let editorDebugElt: DebugElement;

  beforeEach(() => {
    TestBed.configureTestingModule({
      declarations: [ NameEditorComponent, TestHostComponent ]
    });
    fixture = TestBed.createComponent(TestHostComponent);
    testHost = fixture.componentInstance;
    editorDebugElt = fixture.debugElement.query(By.directive(NameEditorComponent));
    fixture.detectChanges();
  });

  it('should capture data', () => {
    const compiled = fixture.debugElement.nativeElement;
    const nameInput = compiled.querySelector('input[type="text"]');
    expect(nameInput).toBeTruthy();
    nameInput.value = 'This is a test';
    fixture.detectChanges();

    // Find submit button
    const submitInput = compiled.querySelector('input[type="submit"]');
    expect(submitInput).toBeTruthy();

    // Trigger click action
    expect(testHost.submitted).toBeFalsy();
    submitInput.click();

    // Submitted
    expect(testHost.submitted).toBe('This is a test');    
  });
});

测试失败，但我不明白为什么。输入中填充了测试结果下方所示的值。任何帮助将不胜感激。

Answer 1

表单提交空值的原因是因为反应式表单是异步的。

编辑表单并在之后立即提交将提交一个空白表单，因为编辑是异步进行的。现在通过添加 500 毫秒的等待时间来通过测试，但很高兴知道如何避免等待：

    // Wait for asynchronous update on reactive form to happen
    setTimeout(() => {

      // Trigger click action
      expect(testHost.submitted).toBeFalsy();
      submitInput.click();

      // Submitted
      expect(testHost.submitted).toBe('This is a test');

    }, 500);

Answer 2

而不是使用“这是一个测试”来检查提交。可以窥探 testHost.submitted 中的 emit 方法，检查它是否被表单控件的值调用。

it('should capture data', () => {
  const compiled = fixture.debugElement.nativeElement;
  spyOn(testHost.submitted, 'emit')
  testHost.name.value('This is a test')
  const submitInput = compiled.querySelector('input[type="submit"]');
  submitInput.click();
  expect(testHost.submitted.emit).toHaveBeenCalled();
  expect(testHost.submitted.emit).toHaveBeenCalledWith(testHost.name.value)
});