如何从单元测试中访问注入的ngControl？

Question

如何从单元测试中访问注入的ngControl？如何解决错误？

在组件中

constructor(
    @Self() @Optional() public ngControl: NgControl
  ) { }

ngOnInit(): void {
    this.ngControl.valueChanges

在单元测试中

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

执行测试时得到错误 TypeError: Cannot read property 'valueChanges' of null

Answer 1

我通过重写解决了这个问题

    beforeEach(async () => {
      const NG_CONTROL_PROVIDER = {
          provide: NgControl,
          useClass: class extends NgControl {
          control = new FormControl();
          viewToModelUpdate() {}
      },
    };

    await TestBed.configureTestingModule({
      declarations: [YourComponentName],
      imports: [FormsModule],
    })
      .overrideComponent(YourComponentName, {
        add: { providers: [NG_CONTROL_PROVIDER] },
      })
      .compileComponents();
  });

Answer 2

适用于：

beforeEach(() => {
     fixture = TestBed.createComponent(?omponent);
     (fixture.componentInstance as any).ngControl = new FormControl();