Question

我是React Hooks的新手，我想实现的目标是测试一个React组件（称为CardFooter），该组件包含对useEffect钩子的调用，该钩子被触发以触发全局上下文变量。

CardFooter.js：

const CardFooter = props => {
  const [localState, setLocalState] = useState({
    attachmentError: false
  });
  const globalContext = useContext(GlobalContext);
  React.useEffect(()=> {
    setLocalState({
    ...localState,
    attachmentError: globalContext.data.attachmentError
  });
 },[globalContext.data.attachmentError]);
}

CardFooter.test.js：

import Enzyme, { shallow } from 'enzyme';    
Enzyme.configure({ adapter: new Adapter() });
describe('<CardFooter  />', () => {
  let useEffect;
  const mockUseEffect = () => {
    useEffect.mockImplementation(f => f());
  };

  useEffect = jest.spyOn(React, "useEffect");
  mockUseEffect(); //

  it('should render correctly with no props.', () => {
  }

  const mockUseEffect = () => {
    useEffect.mockImplementation(f => f());
  };

  useEffect = jest.spyOn(React, "useEffect");
  mockUseEffect();

  const wrapper = shallow(<CardFooter />);
  expect(toJson(wrapper)).toMatchSnapshot();

});

运行测试时出现的错误是：

TypeError: Cannot read property 'attachmentError' of undefined

我尝试了此处介绍的方法：https://medium.com/@pylnata/testing-react-functional-component-using-hooks-useeffect-usedispatch-and-useselector-in-shallow-9cfbc74f62fb。但是，似乎shallow不会选择模拟的useEffect实现。我还尝试模拟useContext和globalContext.data.attachmentError。似乎什么都没有。

Answer 1

试试这个。注意“jest.spyOn”放在“beforeEach”中

  beforeEach(() => {
    jest.spyOn(React, "useEffect").mockImplementationOnce(cb => cb()());
    
     // .... other things ....
  }

jest.spyOn不会嘲笑useEffect挂钩

1 个答案: