我編寫了一個函數，可以在 componentDidMount 觸發時成功測試。但是由于某種原因，使用相同的邏輯來測試其相鄰方法是否已被觸發不起作用。不知道為什么？誰能告訴我我在誤解什么？// Account.js...componentDidMount() {    this.checkData();  }checkData = () => {   console.log('i am a check data method that needs testing');  }...// 是// this works  it('should call the CDM function', () => {    const instance = mountedComponent.instance();    jest.spyOn(instance, 'componentDidMount');    instance.componentDidMount();    expect(instance.componentDidMount).toHaveBeenCalledTimes(1);  })// Attempt 1 - this fails "Cannot spy the checkData property because it is not a function; undefined given instead"  it('should call the `checkData` function', () => {    const instance = mountedComponent.instance();    jest.spyOn(instance, 'checkData');    instance.componentDidMount();    expect(instance.checkData).toBeCalledTimes(1);  })// Attempt 2 - also fails "Received number of calls: 0"  it('should call the `checkData` function', () => {    const instance = mountedComponent.instance();    instance.checkData = jest.fn();    instance.componentDidMount();    expect(instance.checkData).toBeCalledTimes(1);  })為什么 CDM 會出現在實例中而不是checkData？>