Question

学习玩笑和酶以测试反应应用程序，使用create-react-app启动。

在unmount之后使用shallow模拟添加/ removeEventListener崩溃，并在unmount之后使用mount发出警告，请参阅下文。谁知道我做错了什么？

我的测试：

it('should add and remove resize event handler', () => {
  const adder = jest
    .spyOn(global, 'addEventListener')
    .mockImplementation(() => {});
  const remover = jest
    .spyOn(global, 'removeEventListener')
    .mockImplementation(() => {});
  const wrapper = shallow(<App />);
  // this seems to work
  expect(adder).toHaveBeenCalled();
  // causing issues
  wrapper.unmount();
  expect(remover).toHaveBeenCalled();
});

在unmount后使用mount：

  console.error node_modules/fbjs/lib/warning.js:33
    Warning: Can only update a mounted or mounting component. This usually means you called setState, replaceState, or forceUpdate on an unmounted component. This is a no-op.

    Please check the code for the App component.

在unmount后使用shallow：

/home/nik/projects/learn/jest/node_modules/react-scripts/scripts/test.js:20
  throw err;
  ^

Invariant Violation: ReactShallowRenderer render(): Invalid component element.
    at invariant (/home/nik/projects/learn/jest/node_modules/fbjs/lib/invariant.js:42:15)
    at ReactShallowRenderer.render (/home/nik/projects/learn/jest/node_modules/enzyme-adapter-react-16/node_modules/react-test-renderer/cjs/react-test-renderer-shallow.development.js:104:38)
    at Updater.enqueueSetState (/home/nik/projects/learn/jest/node_modules/enzyme-adapter-react-16/node_modules/react-test-renderer/cjs/react-test-renderer-shallow.development.js:329:20)
    at App.Object.<anonymous>.Component.setState (/home/nik/projects/learn/jest/node_modules/react/cjs/react.development.js:237:16)
    at loadData.then.results (/home/nik/projects/learn/jest/src/App.js:15:12)
    at <anonymous>
    at process._tickCallback (internal/process/next_tick.js:188:7)
error An unexpected error occurred: "Command failed.
Exit code: 1
Command: sh
Arguments: -c react-scripts test --env=jsdom
Directory: /home/nik/projects/learn/jest
Output:
".
info If you think this is a bug, please open a bug report with the information provided in "/home/nik/projects/learn/jest/yarn-error.log".
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

Answer 1

我把unmount挂在了诺言

  return Promise.resolve().then(() => {
    wrapper.unmount();
    expect(remover).toHaveBeenCalled();
  });

也错过了错误的线索，'loadData' - 没有嘲笑：

  jest.spyOn(App.prototype, 'loadData')
    .mockImplementation(() => {
      return new Promise(resolve => resolve([topics, subTopics]))
    });

Answer 2

要解决第一个问题，您必须采取措施避免在卸载组件后调用_isMounted。

更简单的方法是在调用setState之前保留componentDidMount() { this._isMounted = true; this.loadData().then(results => { if (!this._isMounted) { return; } const [topics, subTopics, ...rest] = results; this.setState({ topics, subTopics }); }); window.addEventListener('resize', this.someHandler); } componentWillUnmount() { this._isMounted = false; window.removeEventListener('resize', this.someHandler); }标志，然后检查：

    footer {
      position: absolute;
      left: 0;
      bottom: 0;
      width: 100%;
      min-height: 50px;
      line-height: 50px;
      text-align: center;
      margin-top: auto;
      margin-bottom: auto;
      color: white;
      background-color: #232323;
    }
    
    footer a {
      cursor: pointer;
    }
    
    footer a:hover {
      text-decoration: underline;
    }
    
    footer a:not(:last-child)::after {
      content: " | ";
      cursor: default;
    }

您可以阅读有关此问题的更多信息，并在React博客中找到另一种解决方案：https://reactjs.org/blog/2015/12/16/ismounted-antipattern.html

删除了jest /酶测试事件监听器

2 个答案: