如何使用Jest测试异步组件？-Java 学习之路

任何人都可以告诉我如何在安装一个调用 componendDidMount() 的组件时等待一个嘲笑的承诺解决？

class Something extends React.Component {
    state = {
      res: null,
    };

    componentDidMount() {
        API.get().then(res => this.setState({ res }));
    }

    render() {
      if (!!this.state.res) return
      return <span>user: ${this.state.res.user}</span>;
    }
}

API.get() 在我的开玩笑测试中被嘲笑

data = [
  'user': 1,
  'name': 'bob'
];

function mockPromiseResolution(response) {
  return new Promise((resolve, reject) => {
    process.nextTick(
      resolve(response)
    );
  });
}

const API = {
    get: () => mockPromiseResolution(data),
};

然后我的测试文件：

import { API } from 'api';
import { API as mockAPI } from '__mocks/api';

API.get = jest.fn().mockImplementation(mockAPI.get);

describe('Something Component', () => {
  it('renders after data loads', () => {
    const wrapper = mount(<Something />);
    expect(mountToJson(wrapper)).toMatchSnapshot();
    // here is where I dont know how to wait to do the expect until the mock promise does its nextTick and resolves
  });
});

问题是我 expect(mountToJson(wrapper)) 正在返回 null 因为 <Something /> 的模拟api调用和生命周期方法还没有通过 .

1 回答

Jest有假冒伪劣time travelling，在你的情况下使用它，我猜你可以用以下风格改变你的代码：

import { API } from 'api';
import { API as mockAPI } from '__mocks/api';

API.get = jest.fn().mockImplementation(mockAPI.get);

jest.useFakeTimers(); // this statement makes sure you use fake timers

describe('Something Component', () => {
  it('renders after data loads', () => {
    const wrapper = mount(<Something />);

    // skip forward to a certain time
    jest.runTimersToTime(1);

    expect(mountToJson(wrapper)).toMatchSnapshot();
  });
});

作为 jest.runTimersToTime() 的替代，您也可以使用 jest.runAllTimers()

回复于 2024-05-12T16:41:18+08:00

如何使用Jest测试异步组件？

1 回答

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