如何测试使用Jest和Enzyme随时间更新的React组件？

问题描述：

我有这个React组件

I have this React Component

export class Timer extends Component {

constructor(props) {
    super(props);
    this.state = {i : props.i};
}

componentDidMount(){
    this.decrementCounter();
}

decrementCounter(){
    if(this.state.i < 1){
        return;
    }
    setTimeout(() => {
        this.setState({i : this.state.i - 1})
        this.decrementCounter()}, 1000);
}

render(){
    return <span>{this.state.i}</span>
}}

我想表达这样的测试

jest.useFakeTimers();
it('should decrement timer ', () => {
    const wrapper = shallow(<Timer i={10} />);
    expect(wrapper.text()).toBe("10");
    jest.runOnlyPendingTimers();
    expect(wrapper.text()).toBe("9");
});

目前是第一次预期通过，但第二次失败

currently the first expect pass but the second fails

Expected value to be (using ===):
      "9"
    Received:
      "10"

如何正确测试此组件？

How can I properly test this component ?

答

使用完整渲染API，mount（...）

完整DOM渲染对于可能与DOM API交互的组件
的用例非常理想，或者可能需要
命令的完整生命周期才能完全测试组件（即 componentDidMount 等。）

您可以使用 mount（）而不是 shallow（）喜欢

import React from 'react';
import { mount, /* shallow */ } from 'enzyme';
import Timer from './index';

describe('Timer', () => {
    it('should decrement timer ', () => {
        jest.useFakeTimers();

        const wrapper = mount(<Timer i={10} />);
        expect(wrapper.text()).toBe("10");
        jest.runOnlyPendingTimers();
        expect(wrapper.text()).toBe("9");

        jest.useRealTimers();
    });
});

或者您可以将其他对象传递给浅检测它以运行生命周期方法

Or you can pass additional object to shallow to instrument it to run lifecycle methods

请参阅ShallowWrapper.js sourcode

查看浅（）文档

see ShallowWrapper.js sourcode
see shallow() docs

options.disableLifecycleMethods :( Boolean [optional]）：如果设置为true，则不会在组件上调用
componentDidMount，并且在调用后不调用
componentDidUpdate setProps和setContext。

options.disableLifecycleMethods: (Boolean [optional]): If set to true, componentDidMount is not called on the component, and componentDidUpdate is not called after setProps and setContext.

const options = {
  lifecycleExperimental: true,
  disableLifecycleMethods: false 
};

const wrapper = shallow(<Timer i={10} />, options);

我测试了它。它有效。

hinok:~/workspace $ npm test

> c9@0.0.0 test /home/ubuntu/workspace
> jest

 PASS  ./index.spec.js (7.302s)
  Timer
    ✓ should decrement timer  (28ms)

Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        8.162s
Ran all test suites.

如何测试使用Jest和Enzyme随时间更新的React组件？

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