将材料部件作为子组件进行测试

Question

我有一些组件TestComponent，在它的模板中，使用一个<mat-stepper>。由于步骤的上下文，我必须以编程方式进入下一步，而不是在按钮上使用matStepperNext指令。我的组件看起来是这样的：

test.component.ts

import { MatStepper } from '@angular/material/stepper'; //module loaded elsewhere, but is accesible

@Component({
  selector: 'app-test',
  template: '<mat-stepper #stepper>
               <mat-step>
                 <button (click)="completeStep()">Next</button>
               </mat-step>
               <mat-step></mat-step> <!-- etc. -->
             </mat-stepper>',
})
export class TestComponent {
  @ViewChild('stepper') stepper!: MatStepper;

  completeStep() {
    this.stepper.next();
  }
}

现在的诀窍是，我必须测试是否调用了stepper.next()。因为我只是在使用<mat-dialog>指令，所以我从未在类中实际创建它的对象，也没有在构造函数中创建它的提供程序，所以我不太确定如何测试它。我尝试了很多不同的方法，但都没有成功，我最近的测试如下：

test.component.spec.ts

describe('TestComponent', () => {
  let component: TestComponent,
  let fixture: ComponentFixture<TestCompnent>;

  beforeEach(async () => {
    await TestBed.ConfigureTestingModule({
      declarations: [TestComponent],
    }).compileComponents();
  });

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

  describe('completeStep', () => {
    it('should call stepper.next', () => {
      const stepperSpy = jasmine.createSpyObj('MatStepper', ['next']);
      component.stepper = stepperSpy;
      component.completeStep();
      expect(stepperSpy.next).toHaveBeenCalled();
    });
  });
});

但我只是得到了错误

期望间谍MatStepper.next被称为

Answer 1

在每个声明数组之前，将MatStepper添加到声明数组：

beforeEach(async () => {
  await TestBed.ConfigureTestingModule({
       declarations: [TestComponent, MatStepper],
  }).compileComponents();
});

测试用例应该如下所示：

it('completeStep should call stepper.next', () => {     
   jest.spyOn(component.stepper, 'next');
   component.completeStep();
   expect(component.stepper.next).toHaveBeenCalled();
});