我有一个组件，它可以像下面这样查询它的内容子级

@ContentChild(InputControlDirective, { read: ElementRef })
public inputControl: ElementRef;

我有ngAfterContentInit钩子，它检查inputControl是否有值，否则抛出一个自定义错误

public ngAfterContentInit(): void {
        if (!this.inputControl) {
                throw new Error(
                    'Provide a InputControlDirective for the field used with the form-input component like  <input inputControl>'
                );
            }
}

如何在下面的单元测试的ngAfterContentInit钩子之前模拟inputControl？

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

    beforeEach(async () => {
        await TestBed.configureTestingModule({
            imports: [FormInputComponent],
        }).compileComponents();

        fixture = TestBed.createComponent(FormInputComponent);
        component = fixture.componentInstance;
        fixture.detectChanges();
    });

    it('should create', () => {
        expect(component).toBeTruthy();
    });
    });

组件实现是不是使单元测试成为一个挑战？